Adding basic GET tests to the NuCollectionsController spec.
Eliminates the parent getter method, which perfectly replicated already provided functionality from ActiveFedora.
Moves a helper method for minting unique pids into the application controller level, eliminates a bit of the kludginess previously required by nu_collections_controller to successfully create/save a collection object.
Merge branch 'develop' of https://github.com/nu-lts/drs into develop

Merging in changes.