Add posts index and posts controller
Add text to posts index
Add index to routes, remove create from controller

Since this commit is supposed to be limited to displaying a posts index
page, removed the create boilerplate from the controller to keep the
commit cleaner.

Added a posts index only resource to routes.rb
Remove extra newlines

Removed extra lines from posts index, posts_controller, and routes
Merge branch 'lea-posts-index'

* lea-posts-index:
  Remove extra newlines
  Add index to routes, remove create from controller
  Add text to posts index
  Add posts index and posts controller