Creates a partial for displaying a Post's Comments

 new file:   app/views/comments/_comment.html.erb
 modified:   app/views/posts/show.html.erb - nicely DRY'ed
Adds a partial template for creating a public Comment attached to a Post

 new file:   app/views/posts/_comment_form.html.erb
 modified:   app/views/posts/show.html.erb
Creates a partial template for rendering errors and DRY's up admin forms

 new file:   app/views/shared/_error_messages.html.erb - partial in question

 modified:   app/views/admin/comments/_form.html.erb - render the shared error partial
 modified:   app/views/admin/posts/_form.html.erb
 modified:   app/views/admin/users/_form.html.erb
Creates nested resource for Comments

 modified:   config/routes.rb - only allow create action
Creates Comment controller with create action

 new file:   app/controllers/comments_controller.rb - creates a comment using params from
              comment form and if valid saves
 modified:   app/controllers/posts_controller.rb - Post show action passes an empty Comment
              to the view
 modified:   app/views/posts/_comment_form.html.erb - creates the form for the comment passed
              from the Post show action, includes shared error messages partial
 modified:   app/views/posts/show.html.erb - as the Comments controller calls 'posts/show'
              when the comment does not save, the location of the partials is explicitly
              set or else the controller looks for them in the app/views/comments folder
Adds descriptive span elements to Comment form

 modified:   app/views/posts/_comment_form.html.erb - marks required fields and
              puts inputs in separate divs
Displays comment creation date in Twitter style #{time} ago

 modified:   app/views/comments/_comment.html.erb
Introduces a `url` field to Comment model

 new file:   db/migrate/20131214110942_add_url_to_comments.rb
 modified:   db/schema.rb

 modified:   spec/models/comment_spec.rb - updated spec
 modified:   spec/factories.rb
Adds new Comment.url field to Comment form

 modified:   app/views/posts/_comment_form.html.erb
Creates helper to prepend http protocol when missing from a URL

 new file:   app/helpers/url_helper.rb
 new file:   spec/helpers/url_helper_spec.rb
Uses new url_with_protocol helper in Comment partial

 modified:   app/views/comments/_comment.html.erb
Merge branch 'public-comments' into develop-blog

 Creates shared partial for displaying form errors, DRYs admin forms too
 Creates partial for displaying Comments attached to a Post and other elements
 Creates nested resource for Comments
 Adds `url` field to Comment model
 Creates helper method to prepend http protocol to urls without it