Render empty json on Sessions#destroy
Merge pull request #16 from neighborly/im-sessions-destroy-render-empty-json

Render empty json on Sessions#destroy
Rename api constraint version to revision
Register json api mime type
Fix apiary doc and add revision header to sessions
[DOC] Add body section to create a new session
Include all ActionController modules in our BaseController

During development of the gem, its easier to simply go with the default
controller by default. Remove those not used when releasing the first
version in the RubyGems.
Add rabl as dependency
Respond to GET /users/:id to show users' data
Use "user" as top level node of GET /users/:id
Follow RFC 3339 for date time responses