Fix predicate_mappings.yml file path for generator
Testing and handling Groups Controller error

If an error was encountered on the either create or update, the @group
instance variable was not being set and instead would throw an error.
Adjusting Group Membership user comparison

By using User#user_key, we are allowing the behavior for implementors
that chose to use a username as the identifier.

@TODO - need to craft the GroupMembership idea. When we iterate on a
Groups#members, we should be providing a proper object that can be
more easily interrogated for its responsibilities.
Merge pull request #536 from projecthydra-labs/feature/fix-predicate-mapping-file-path-for-generator

Fix predicate_mappings.yml file path for generator
Merge pull request #537 from ndlib/updating-group-error-handling

Testing and handling Groups Controller error
Merge pull request #538 from ndlib/associating-groups-user-key

Adjusting Group Membership user comparison
Merge branch 'develop' into curate-nd-beta

* develop:
  Adjusting Group Membership user comparison
  Testing and handling Groups Controller error
  Fix predicate_mappings.yml file path for generator