posts destruction depends on admins
require posts admin_id to be present
add posts specs
add post specs
add tags to posts factory
add tags to posts table
add validation for tags in Post model
fix typo in post_spec.rb
add subscription_needed? method to post model
add index to tags
fix destroy dependency for posts and admins
remove attr_accessor for posts tags
configur post controller to handle tags
add tags text field to post form
add show method to posts controller
add posts show view
add posts show link to last_posts
add posts show route
use activerecord validation helpers for tags
define and use TAG_SEPERATOR constant