Added in a new mixing - UserControllerMixins.

We have changed the name of the original ControllerMixins to
GlobalUserMixins because these are fucntions that can be used in
both testing and in general code.

We then created a new mixin called UserControllerMixins that
deals with the basic create, show, update and destroy to
abstract out some of the logic.

We then updated the application_controller and spec_helper
files to reflect these changes.