move concerns to the model/concerns
It's these COLONS! HE HATES THESE COLONS!

https://www.youtube.com/watch?v=Tcwz8-EfFYE
Factor out mocks
Merge pull request #2279 from fantasticfears/concern

move concerns to the model/concerns
move custom fields into its own concern
Add CustomFields to Post, Category and Group
fix double save missing error by using copy not actual reference
Add Custom Fields on Topics
Add Support for Arrays to CustomFields
Move Concern from lib into app/models. refs #2279