Update & grunt-groc and fix docs errors

issue #2622

- Updated grunt-groc to 0.4.5
- Fixed the few places which made the docs fail to generate
- There is still a mix of styles
Made better-er
Post API response to use author not author_id

Closes #2608
- added toJSON method override for post model
- in the event no expanded author relation is present the id will be used
- removed author_id from expected response JSON for posts.
- updated integration tests to check for existence or not of author and author_id