Created Tag model
Created tag factory
Added validators to Tag
Created PostTag model
Added associations to PostTag
Added tag_line field to Post model
Created TagParser
Created TagLineValidator
Added TagLineValidator to Post
Added associations to Post
Renamed fields of PostTag
Added activerecord-import gem
Added method to rebuild tags_posts after save post
Added tag_line field in admin Post form
Added scope tagged_with to Post
Added action index_by_tag to PostsController
Updated routes for root