Added requirements.txt, setting for doc_expansion

Currently, the `docExpansion` param in the swagger-ui object is hardcoded to the default ( `docExpansion: "none"`). In my use case I only have a few endpoints in my API so I wanted to override the setting to `docExpansion: "full"`. 

I made the following changes:
 - Added it to the default settings
 - Passed it into the requestContext in the view
 - Updated the template to pull from the settings
 - Updated the settings page of the docs to include the new param
 - Added a requirements.txt file so it's easy to install the test dependencies when creating PRs