For #20562, implement 'followers' support in python-api.
For #22789, make python api follow tests do nothing if the server version is earlier than 5.2.
For #20562, better approach to making python api tests version specific.
For #20562, rewrite python api unit tests for follow to fit python api unit test conventions.
Merge pull request #53 from shotgunsoftware/20562_api_follow

For #20562, implement 'followers' support in python-api.