Pipenv install can't handle spaces in windows user folder
Hi there, I've poked my head in on this project to check it out, but I'm having some trouble on my work machine.

##### Describe your environment

1. Windows 10 Pro
1. Python version: Python 3.6.4
1. Pipenv version: pipenv, version 11.1.5
1. Happens in both Powershell and CMD, but not in bash (probably due to Linux Subsystem for Windows uses a different home directory path, that doesn't have spaces in the name)

##### Expected result

pipenv to create the environment

##### Actual result
```
PS D:\\Projects\\Django\\feedback> pipenv --verbose install
Error: no such option: --verbose
PS D:\\Projects\\Django\\feedback> pipenv install --verbose
Creating a Pipfile for this project…
Pipfile.lock not found, creating…
Locking [dev-packages] dependencies…

'C:\\Users\\First' is not recognized as an internal or external command,
operable program or batch file.
```

I've removed my actual name from the output, but to add here, my user folder path is 
"C:\\Users\\First Last\\"

##### Steps to replicate

 1. cd D:\\Projects\\Django\\feedback
 1. pipenv install --verbose

diff --git a/pipenv/core.py b/pipenv/core.py
index 7971b338..e54ce80c 100644
--- a/pipenv/core.py
+++ b/pipenv/core.py
@@ -33,7 +33,7 @@ from requests.packages.urllib3.exceptions import InsecureRequestWarning
 from .project import Project
 from .utils import (
     convert_deps_from_pip, convert_deps_to_pip, is_required_version,
-    proper_case, pep423_name, split_file, merge_deps, venv_resolve_deps, shellquote, is_vcs,
+    proper_case, pep423_name, split_file, merge_deps, venv_resolve_deps, escape_grouped_arguments, is_vcs,
     python_version, find_windows_executable, is_file, prepare_pip_source_args,
     temp_environ, is_valid_url, download_file, get_requirement, need_update_check,
     touch_update_stamp, is_pinned, is_star, TemporaryDirectory
@@ -217,7 +217,7 @@ def ensure_latest_pip():
 
     # Ensure that pip is installed.
     try:
-        c = delegator.run('"{0}" install pip'.format(which_pip()))
+        c = delegator.run('{0} install pip'.format(escape_grouped_arguments(which_pip())))
 
         # Check if version is out of date.
         if 'however' in c.err:
@@ -226,7 +226,7 @@ def ensure_latest_pip():
 
             windows = '-m' if os.name == 'nt' else ''
 
-            c = delegator.run('"{0}" install {1} pip --upgrade'.format(which_pip(), windows), block=False)
+            c = delegator.run('{0} install {1} pip --upgrade'.format(escape_grouped_arguments(which_pip()), windows), block=False)
             click.echo(crayons.blue(c.out))
     except AttributeError:
         pass
@@ -1013,8 +1013,8 @@ def get_downloads_info(names_map, section):
         version = parse_download_fname(fname, name)
 
         # Get the hash of each file.
-        cmd = '"{0}" hash "{1}"'.format(
-            which_pip(),
+        cmd = '{0} hash "{1}"'.format(
+            escape_grouped_arguments(which_pip()),
             os.sep.join([project.download_location, fname])
         )
 
@@ -1102,7 +1102,7 @@ def do_lock(verbose=False, system=False, clear=False, pre=False, keep_outdated=F
     # Add refs for VCS installs.
     # TODO: be smarter about this.
     vcs_deps = convert_deps_to_pip(project.vcs_dev_packages, project, r=False)
-    pip_freeze = delegator.run('{0} freeze'.format(which_pip())).out
+    pip_freeze = delegator.run('{0} freeze'.format(escape_grouped_arguments(which_pip()))).out
 
     if vcs_deps:
         for line in pip_freeze.strip().split('\\n'):
@@ -1262,7 +1262,7 @@ def do_purge(bare=False, downloads=False, allow_global=False, verbose=False):
         shutil.rmtree(project.download_location)
         return
 
-    freeze = delegator.run('"{0}" freeze'.format(which_pip(allow_global=allow_global))).out
+    freeze = delegator.run('{0} freeze'.format(escape_grouped_arguments(which_pip(allow_global=allow_global)))).out
 
     # Remove comments from the output, if any.
     installed = [line for line in freeze.splitlines() if not line.lstrip().startswith('#')]
@@ -1290,7 +1290,7 @@ def do_purge(bare=False, downloads=False, allow_global=False, verbose=False):
 
     if not bare:
         click.echo(u'Found {0} installed package(s), purging…'.format(len(actually_installed)))
-    command = '"{0}" uninstall {1} -y'.format(which_pip(allow_global=allow_global), ' '.join(actually_installed))
+    command = '{0} uninstall {1} -y'.format(escape_grouped_arguments(which_pip(allow_global=allow_global)), ' '.join(actually_installed))
 
     if verbose:
         click.echo('$ {0}'.format(command))
@@ -1416,7 +1416,7 @@ def pip_install(
 
         # Don't specify a source directory when using --system.
         if not allow_global and ('PIP_SRC' not in os.environ):
-            src = '--src {0}'.format(shellquote(project.virtualenv_src_location))
+            src = '--src {0}'.format(escape_grouped_arguments(project.virtualenv_src_location))
         else:
             src = ''
     else:
@@ -1454,7 +1454,7 @@ def pip_install(
         pre = '--pre' if pre else ''
 
         quoted_pip = which_pip(allow_global=allow_global)
-        quoted_pip = shellquote(quoted_pip)
+        quoted_pip = escape_grouped_arguments(quoted_pip)
         upgrade_strategy = '--upgrade-strategy=only-if-needed' if selective_upgrade else ''
 
         pip_command = '{0} install {4} {5} {6} {7} {3} {1} {2} --exists-action w'.format(
@@ -1481,8 +1481,8 @@ def pip_install(
 
 def pip_download(package_name):
     for source in project.sources:
-        cmd = '"{0}" download "{1}" -i {2} -d {3}'.format(
-            which_pip(),
+        cmd = '{0} download "{1}" -i {2} -d {3}'.format(
+            delegator.run(which_pip()),
             package_name,
             source['url'],
             project.download_location
@@ -1499,7 +1499,7 @@ def which_pip(allow_global=False):
         if 'VIRTUAL_ENV' in os.environ:
             return which('pip', location=os.environ['VIRTUAL_ENV'])
 
-        for p in ('pip', 'pip2', 'pip3'):
+        for p in ('pip', 'pip3', 'pip2'):
             where = system_which(p)
             if where:
                 return where
@@ -2226,7 +2226,7 @@ def do_check(three=None, python=False, system=False, unused=False, args=None):
         python = which('python')
 
     # Run the PEP 508 checker in the virtualenv.
-    c = delegator.run('"{0}" {1}'.format(python, shellquote(pep508checker.__file__.rstrip('cdo'))))
+    c = delegator.run('"{0}" {1}'.format(python, escape_grouped_arguments(pep508checker.__file__.rstrip('cdo'))))
     results = simplejson.loads(c.out)
 
     # Load the pipfile.
@@ -2267,7 +2267,7 @@ def do_check(three=None, python=False, system=False, unused=False, args=None):
     else:
         python = system_which('python')
 
-    c = delegator.run('"{0}" {1} check --json --key=1ab8d58f-5122e025-83674263-bc1e79e0'.format(python, shellquote(path)))
+    c = delegator.run('"{0}" {1} check --json --key=1ab8d58f-5122e025-83674263-bc1e79e0'.format(python, escape_grouped_arguments(path)))
     try:
         results = simplejson.loads(c.out)
     except ValueError:
@@ -2338,7 +2338,7 @@ def do_graph(bare=False, json=False, reverse=False):
 
     cmd = '"{0}" {1} {2}'.format(
         python_path,
-        shellquote(pipdeptree.__file__.rstrip('cdo')),
+        escape_grouped_arguments(pipdeptree.__file__.rstrip('cdo')),
         flag
     )
 
diff --git a/pipenv/utils.py b/pipenv/utils.py
index be2f4dc0..89872f00 100644
--- a/pipenv/utils.py
+++ b/pipenv/utils.py
@@ -209,8 +209,11 @@ def python_version(path_to_python):
     return u"{v[0]}.{v[1]}.{v[2]}".format(v=parsed)
 
 
-def shellquote(s):
-    """Prepares a string for the shell (on Windows too!)"""
+def escape_grouped_arguments(s):
+    """Prepares a string for the shell (on Windows too!)
+
+    Only for use on grouped arguments (passed as a string to Popen)
+    """
     if s is None:
         return None
     # Additional escaping for windows paths
@@ -348,8 +351,8 @@ def venv_resolve_deps(deps, which, project, pre=False, verbose=False, clear=Fals
     from . import resolver
     import json
 
-    resolver = shellquote(resolver.__file__.rstrip('co'))
-    cmd = '{0} {1} {2} {3}'.format(which('python'), resolver, '--pre' if pre else '', '--verbose' if verbose else '')
+    resolver = escape_grouped_arguments(resolver.__file__.rstrip('co'))
+    cmd = '{0} {1} {2} {3}'.format(escape_grouped_arguments(which('python')), resolver, '--pre' if pre else '', '--verbose' if verbose else '')
     os.environ['PIPENV_PACKAGES'] = '\\n'.join(deps)
 
     c = delegator.run(cmd, block=True)
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 8e748cd1..7328409e 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -185,7 +185,7 @@ class TestUtils:
     def test_windows_shellquote(self):
         test_path = 'C:\\Program Files\\Python36\\python.exe'
         expected_path = '"C:\\\\\\\\Program Files\\\\\\\\Python36\\\\\\\\python.exe"'
-        assert pipenv.utils.shellquote(test_path) == expected_path
+        assert pipenv.utils.escape_grouped_arguments(test_path) == expected_path
 
     @pytest.mark.utils
     def test_is_valid_url(self):
['pipenv/core.py', 'pipenv/utils.py', 'tests/test_utils.py']