Remove decryption debug logging
Allow collaborator to leave bucket. Refs #45

* If the authenticating user sends  a DELETE
buckets/:id/collaborators/:account_id, the user is
removed from the list of collaborators (if they are collaborating
on the bucket with the specified id)

* DELETE buckets/:id/collaborators now uses the
account_id parameter
Allow collaborator to leave river

* The authenticated user is now able to remove themselves
from the list of a river's collaborators

* DELETE rivers/:id/collaborators accepts the account_id
of the collaborator; not the colloborator_id. The same
applies for PUT rivers/:id/collaborators

* Closes #45
Doc blocks and source formatting
Merge pull request #46 from ushahidi/collaboration-dev

Collaboration dev