Refactoring (directory organization) for acts_as_taggable (wincent.dev, 36d2f80)

Switched over a number of model classes to use acts_as_taggable and re-organized some of the subfolders to make the inclusion a little neater (requiring "active_record/acts/taggable" rather than "taggable").

Signed-off-by: Greg Hurrell <greg@hurrell.net>