New Data Model commits, squashed into one.
Implementing tagging for the Question model.

Implementing tagging for the Question model.
Restored breadcrumbs to Tag pages
Restored breadcrumbs for answers pages
Added json views for tags API
added basic view specs for tags
Removed unneeded json views for questions (non api)
Added mocks to tags controller spec
Merge pull request #203 from 18F/feature/tagging_sensibly_squashed

Feature/tagging sensibly squashed