resolves#2170
- creates a models.init() function that requires all other model files
and caches them. This is opposed to the previous functionality where
when you require('./models') it would immediately require all other models.
Now it's done when you want.
- Updates all tests to reflect the new structure of the model module
Closes#2866
-update slug API to handle users and apps in addition to
posts and tags
-update existing tests
-add new functional tests for slug endpoint on http api
Closes#2601
- Removed slug generation from the post API
- Added new, self-contained slug API
- Fixed slug permissions in the fixtures files
- Added a HTTP route for the new API method
- Added integrational tests
