Pipenv unexpectedly installs from requirements.txt (even from parent directories)
This was a weird one and it was so odd that I thought I was losing my mind for a bit. ;-) Thanks for pipenv though, I'm very excited about this new direction!

Pipenv installs requirements.txt when you don't ask it to, and when it try to keep it from installing them, it still does. This is on Windows 10. Not sure if reproduces on Linux\\OSx

`$ python -m pipenv.help`

<details><summary>$ python -m pipenv.help output</summary>

Pipenv version: `'2018.05.18'`

Pipenv location: `'C:\\\\Users\\\\patri\\\\AppData\\\\Local\\\\Programs\\\\Python\\\\Python36\\\\lib\\\\site-packages\\\\pipenv'`

Python location: `'C:\\\\Users\\\\patri\\\\AppData\\\\Local\\\\Programs\\\\Python\\\\Python36\\\\python.exe'`

Other Python installations in `PATH`:

  - `3.6`: `C:\\Users\\patri\\AppData\\Local\\Programs\\Python\\Python36\\python.exe`

  - `3.6.5`: `C:\\Users\\patri\\AppData\\Local\\Programs\\Python\\Python36\\python.exe`
  - `3.6.5`: `C:\\Windows\\py.exe`

PEP 508 Information:

```
{'implementation_name': 'cpython',
 'implementation_version': '3.6.5',
 'os_name': 'nt',
 'platform_machine': 'AMD64',
 'platform_python_implementation': 'CPython',
 'platform_release': '10',
 'platform_system': 'Windows',
 'platform_version': '10.0.17134',
 'python_full_version': '3.6.5',
 'python_version': '3.6',
 'sys_platform': 'win32'}
```

System environment variables:

  - `ALLUSERSPROFILE`
  - `APPDATA`
  - `COMMONPROGRAMFILES`
  - `COMMONPROGRAMFILES(X86)`
  - `COMMONPROGRAMW6432`
  - `COMPUTERNAME`
  - `COMSPEC`
  - `DRIVERDATA`
  - `GDAL_DATA`
  - `HOMEDRIVE`
  - `HOMEPATH`
  - `LOCALAPPDATA`
  - `LOGONSERVER`
  - `NUMBER_OF_PROCESSORS`
  - `ONEDRIVE`
  - `OS`
  - `OSGEO4W_ROOT`
  - `PATH`
  - `PATHEXT`
  - `POSTGIS_ENABLE_OUTDB_RASTERS`
  - `POSTGIS_GDAL_ENABLED_DRIVERS`
  - `PROCESSOR_ARCHITECTURE`
  - `PROCESSOR_IDENTIFIER`
  - `PROCESSOR_LEVEL`
  - `PROCESSOR_REVISION`
  - `PROGRAMDATA`
  - `PROGRAMFILES`
  - `PROGRAMFILES(X86)`
  - `PROGRAMW6432`
  - `PROJ_LIB`
  - `PROMPT`
  - `PSMODULEPATH`
  - `PUBLIC`
  - `SESSIONNAME`
  - `SYSTEMDRIVE`
  - `SYSTEMROOT`
  - `TEMP`
  - `TMP`
  - `USERDOMAIN`
  - `USERDOMAIN_ROAMINGPROFILE`
  - `USERNAME`
  - `USERPROFILE`
  - `VS140COMNTOOLS`
  - `WINDIR`
  - `PYTHONDONTWRITEBYTECODE`
  - `PIP_PYTHON_PATH`

Pipenv–specific environment variables:


Debug–specific environment variables:

  - `PATH`: `C:\\Program Files (x86)\\Intel\\Intel(R) Management Engine Components\\iCLS\\;C:\\Program Files\\Intel\\Intel(R) Management Engine Components\\iCLS\\;C:\\Program Files (x86)\\Common Files\\Oracle\\Java\\javapath;C:\\Program Files (x86)\\Windows Resource Kits\\Tools\\;C:\\ProgramData\\Oracle\\Java\\javapath;C:\\Program Files\\Dell\\DW WLAN Card;C:\\Windows\\system32;C:\\Windows;C:\\Windows\\System32\\Wbem;C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\syswow64;C:\\Program Files (x86)\\NVIDIA Corporation\\PhysX\\Common;C:\\Users\\patri\\Tools\\;C:\\Program Files (x86)\\Windows Kits\\10\\Windows Performance Toolkit\\;C:\\WINDOWS\\system32;C:\\WINDOWS;C:\\WINDOWS\\System32\\Wbem;C:\\WINDOWS\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\Git\\cmd;C:\\Program Files (x86)\\Microsoft VS Code\\bin;C:\\Program Files\\Amazon\\AWSCLI;C:\\Users\\patri\\AppData\\Local\\GitHub\\PortableGit_d76a6a98c9315931ec4927243517bc09e9b731a0\\cmd;C:\\Users\\patri\\AppData\\Local\\Microsoft\\WindowsApps;C:\\Program Files (x86)\\Nmap;C:\\Users\\patri\\AppData\\Roaming\\npm;C:\\Program Files\\Heroku\\bin;C:\\OSGeo4W64\\bin;c:\\Program Files (x86)\\Microsoft SQL Server\\100\\Tools\\Binn\\;c:\\Program Files\\Microsoft SQL Server\\100\\Tools\\Binn\\;c:\\Program Files\\Microsoft SQL Server\\100\\DTS\\Binn\\;C:\\WINDOWS\\system32;C:\\WINDOWS;C:\\WINDOWS\\System32\\Wbem;C:\\WINDOWS\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files (x86)\\Intel\\Intel(R) Management Engine Components\\DAL;C:\\Program Files\\Intel\\Intel(R) Management Engine Components\\DAL;C:\\Program Files (x86)\\Intel\\Intel(R) Management Engine Components\\IPT;C:\\Program Files\\Intel\\Intel(R) Management Engine Components\\IPT;C:\\Program Files\\Amazon\\AWSCLI\\bin\\;C:\\WINDOWS\\System32\\OpenSSH\\;c:\\users\\patri\\appdata\\local\\programs\\python\\python36\\Scripts;C:\\Users\\patri\\AppData\\Local\\Programs\\Python\\Python36\\Scripts\\;C:\\Users\\patri\\AppData\\Local\\Programs\\Python\\Python36\\;C:\\Program Files\\Amazon\\AWSCLI;C:\\Users\\patri\\AppData\\Local\\GitHub\\PortableGit_d76a6a98c9315931ec4927243517bc09e9b731a0\\cmd;C:\\Users\\patri\\AppData\\Local\\Microsoft\\WindowsApps;C:\\Program Files (x86)\\Nmap;C:\\Program Files\\Heroku\\bin;C:\\Users\\patri\\AppData\\Local\\Microsoft\\WindowsApps;C:\\Program Files\\Microsoft VS Code\\bin;C:\\Users\\patri\\AppData\\Local\\Pandoc\\;`


---------------------------

Contents of `Pipfile` ('C:\\\\Users\\\\patri\\\\code\\\\local\\\\piptest\\\\Pipfile'):

```toml
[[source]]
url = "https://pypi.org/simple"
verify_ssl = true
name = "pypi"

[packages]
nflgame = "==1.2.20"
requests = "*"

[dev-packages]

[requires]
python_version = "3.6"

```


Contents of `Pipfile.lock` ('C:\\\\Users\\\\patri\\\\code\\\\local\\\\piptest\\\\Pipfile.lock'):

```json
{
    "_meta": {
        "hash": {
            "sha256": "dd4fd0a58e50c39e99da316cc62783d7f58d2a7cfd3fdf5965233e3fcef3f88d"
        },
        "pipfile-spec": 6,
        "requires": {
            "python_version": "3.6"
        },
        "sources": [
            {
                "name": "pypi",
                "url": "https://pypi.org/simple",
                "verify_ssl": true
            }
        ]
    },
    "default": {
        "beautifulsoup4": {
            "hashes": [
                "sha256:11a9a27b7d3bddc6d86f59fb76afb70e921a25ac2d6cc55b40d072bd68435a76",
                "sha256:7015e76bf32f1f574636c4288399a6de66ce08fb7b2457f628a8d70c0fbabb11",
                "sha256:808b6ac932dccb0a4126558f7dfdcf41710dd44a4ef497a0bb59a77f9f078e89"
            ],
            "version": "==4.6.0"
        },
        "certifi": {
            "hashes": [
                "sha256:13e698f54293db9f89122b0581843a782ad0934a4fe0172d2a980ba77fc61bb7",
                "sha256:9fa520c1bacfb634fa7af20a76bcbd3d5fb390481724c597da32c719a7dca4b0"
            ],
            "version": "==2018.4.16"
        },
        "chardet": {
            "hashes": [
                "sha256:84ab92ed1c4d4f16916e05906b6b75a6c0fb5db821cc65e70cbd64a3e2a5eaae",
                "sha256:fc323ffcaeaed0e0a02bf4d117757b98aed530d9ed4531e3e15460124c106691"
            ],
            "version": "==3.0.4"
        },
        "httplib2": {
            "hashes": [
                "sha256:e71daed9a0e6373642db61166fa70beecc9bf04383477f84671348c02a04cbdf"
            ],
            "version": "==0.11.3"
        },
        "idna": {
            "hashes": [
                "sha256:2c6a5de3089009e3da7c5dde64a141dbc8551d5b7f6cf4ed7c2568d0cc520a8f",
                "sha256:8c7309c718f94b3a625cb648ace320157ad16ff131ae0af362c9f21b80ef6ec4"
            ],
            "version": "==2.6"
        },
        "nflgame": {
            "hashes": [
                "sha256:0a9852009f71870ac3e44e9aeca4f4664c76accd2353fc7c4c9dd42f83e163a7",
                "sha256:1015675386dd97341f02e1614ef79f8b162cb2826bbddc8c2fec3de0eff20055"
            ],
            "index": "pypi",
            "version": "==1.2.20"
        },
        "pytz": {
            "hashes": [
                "sha256:65ae0c8101309c45772196b21b74c46b2e5d11b6275c45d251b150d5da334555",
                "sha256:c06425302f2cf668f1bba7a0a03f3c1d34d4ebeef2c72003da308b3947c7f749"
            ],
            "version": "==2018.4"
        },
        "requests": {
            "hashes": [
                "sha256:6a1b267aa90cac58ac3a765d067950e7dbbf75b1da07e895d1f594193a40a38b",
                "sha256:9c443e7324ba5b85070c4a818ade28bfabedf16ea10206da1132edaa6dda237e"
            ],
            "index": "pypi",
            "version": "==2.18.4"
        },
        "urllib3": {
            "hashes": [
                "sha256:06330f386d6e4b195fbfc736b297f58c5a892e4440e54d294d7004e3a9bbea1b",
                "sha256:cc44da8e1145637334317feebd728bd869a35285b93cbb4cca2577da7e62db4f"
            ],
            "version": "==1.22"
        }
    },
    "develop": {}
}

```
</details>
------------

##### Expected result
pipenv install <library> should NOT install anything else other than library & dependencies.
pipenv install <library> should not install requirements.txt when requirements.txt has been moved (from the repro and not commited)

##### Actual result
pipenv installs requirements.txt when it exists and its not asked to.
pipenv installs requirement.txt when it is deleted and the change is not commited to the repro

When possible, provide the verbose output (`--verbose`), especially for locking and dependencies resolving issues.

##### Steps to replicate
1. Git init new_repro
2. Create requirements.txt and add a library (nflgame==1.2.20 for example)
3. Don't pip install or pipenv install anything at this point.
4.. Add and Commit requirements.txt to the repro
5. move requirements.txt out of the repro.
.6 pipenv install some other library (`pipenv install requests`)

The library in the requirements.txt is installed
```
pipenv graph
nflgame==1.2.20
  - beautifulsoup4 [required: Any, installed: 4.6.0]
  - httplib2 [required: Any, installed: 0.11.3]
  - pytz [required: Any, installed: 2018.4]
requests==2.18.4
  - certifi [required: >=2017.4.17, installed: 2018.4.16]
  - chardet [required: >=3.0.2,<3.1.0, installed: 3.0.4]
  - idna [required: <2.7,>=2.5, installed: 2.6]
  - urllib3 [required: <1.23,>=1.21.1, installed: 1.22]
``

diff --git a/pipenv/core.py b/pipenv/core.py
index 504ce47e..da39de5e 100644
--- a/pipenv/core.py
+++ b/pipenv/core.py
@@ -1779,7 +1779,8 @@ def do_install(
         keep_outdated = True
     more_packages = more_packages or []
     # Don't search for requirements.txt files if the user provides one
-    skip_requirements = True if requirements else False
+    if requirements or package_name or project.pipfile_exists:
+        skip_requirements = True
     concurrent = (not sequential)
     # Ensure that virtualenv is available.
     ensure_project(
['pipenv/core.py']