wip
added tests for popular tags
added tags to the view and model method
some tweaks after rebasing master, refactor some specs regarding the most popular tags functionality
Merge pull request #27 from tangosource/feature/as-a-user-i-should-be-able-to-see-the-most-popular-tags

feature/as-a-user-i-should-be-able-to-see-the-most-popular-tags