Fix mlagents re-install directions

- Fix re-install directions to include -e modifer
- Move re-install directions from creating-custom... to protobuf readme
- Add how to see confirmation that install worked

docs/Creating-Custom-Protobuf-Messages.md

 
 ## Implementing a Custom Message
 
-Assume the ml-agents repository is checked out to a folder named $MLAGENTS_ROOT. Whenever you change the fields of a custom message, you must run `$MLAGENTS_ROOT/protobuf-definitions/make.bat` (for Windows, use `make_for_win.bat`) to create C# and Python files corresponding to the new message. Follow the directions in [this file](../protobuf-definitions/README.md) for guidance. After running `$MLAGENTS_ROOT/protobuf-definitions/make.bat`, reinstall the Python package by running `pip install $MLAGENTS_ROOT/ml-agents` and make sure your Unity project is using the newly-generated version of `$MLAGENTS_ROOT/UnitySDK`.
+Whenever you change the fields of a custom message, you must follow the directions in [this file](../protobuf-definitions/README.md) to create C# and Python files corresponding to the new message and re-install the mlagents Python package.
 
 ## Custom Message Types
 

protobuf-definitions/README.md

 
 ## Set-up & Installation
 
-Assume the ml-agents repository is checked out to a folder named $MLAGENTS_ROOT.
+Assume the ml-agents repository is checked out to a folder named $MLAGENTS_ROOT.
 **Note:** If you're using Anaconda, don't forget to activate the ml-agents environment first.
 
 `pip install protobuf==3.6.0 --force`
  ```
 This is to make sure the generated code does not try to access the Grpc library
 on platforms that are not supported by Grpc.
+
+Finally, re-install the mlagents packages by running the following commands from the same `$MLAGENTS_ROOT\protobuf-definitions` directory.
+
+```
+cd ..
+cd ml-agents-envs
+pip install -e .
+cd ..
+cd ml-agents
+pip install -e .
+mlagents-learn
+```
+
+The final line will test if everything was generated and installed correctly. If it worked, you should see the Unity logo.