`brownie bake` fails if the mix name capitalization does not match exactly
### Environment information

* `brownie` Version: 1.11.10
* `ganache-cli` Version: v6.9.1 (ganache-core: 2.10.2)
* `solc` Version: 0.7.4
* Python Version: 3.8.6
* OS: linux

### What was wrong?
Simply running `brownie bake` fails if the mix name is improperly capitalized.

```bash
brownie bake Token
```
Output:
```
Brownie v1.11.10 - Python development framework for Ethereum

Downloading from https://github.com/brownie-mix/Token-mix/archive/master.zip...
9.13kiB [00:00, 3.79MiB/s]
  File "brownie/_cli/__main__.py", line 64, in main
    importlib.import_module(f"brownie._cli.{cmd}").main()
  File "brownie/_cli/bake.py", line 26, in main
    path = project.from_brownie_mix(args["<mix>"], args["<path>"], args["--force"])
  File "brownie/project/main.py", line 577, in from_brownie_mix
    project_path.parent.joinpath(project_name + "-mix-master").rename(project_path)
  File "/usr/lib/python3.8/pathlib.py", line 1361, in rename
    self._accessor.rename(self, target)
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/Token-mix-master' -> '/tmp/Token'
```

### How can it be fixed?
`brownie` should either normalize the name to lower case or (if the case could be significant) report that such a mix does not exist, hinting at the case as a possible cause.
diff --git a/brownie/project/main.py b/brownie/project/main.py
index 4aeabbf8..24e28b6d 100644
--- a/brownie/project/main.py
+++ b/brownie/project/main.py
@@ -564,7 +564,7 @@ def from_brownie_mix(
 
     Returns the path to the project as a string.
     """
-    project_name = str(project_name).replace("-mix", "")
+    project_name = str(project_name).lower().replace("-mix", "")
     url = MIXES_URL.format(project_name)
     if project_path is None:
         project_path = Path(".").joinpath(project_name)
['brownie/project/main.py']