Use post_params for post update
Merge branch 'assignment-1'

* assignment-1:
  Use post_params for post update
  Fix permitted params on comment controller
  Link to posts_new from posts_index
  Add authentication for unsafe actions
  Let users delete comments
  Extract comment form into a partial
  Extract comment into a partial
  Add comments to posts
  Let users delete posts
  Make edit page and create _form partial
  Let users update posts
  Validate post title presence and length
  Add simple CRUD for posts
  Create a root page