Ignore Vim swapfiles
Create Relationship model

The Relationship model represents the notion of users following one
another. Each row in the table is a connection between two users, one
following the other.

* Create the :relationships table
* Add indices for each of the columns
* Ensure that rows are unique
Define User/Relationship associations

* Mark User as having many Relationships
* Make Relationships dependent on User
* Mark Relationship as belonging to :follower and :followed
Add validations to Relationship

* Validate the presence of :follower_id
* Validate the presence of :followed_id
Add followed_users association

* Add the followed_users association (through relationships)
* Add utility methods for following, unfollowing and checking for
  relationship
Add followers associations

* Add the reverse_relationships association
* Add followers association through reverse_relationships
Prepare sample data

* Rewrite sample_data rake task
* Create users, microposts, and relationships
Add stats and follow form

* Add :following and :followers routes to :users
* Add a partial for displaying follower stats
* Add a partial for a follow/unfollow form
* Add routes for user relationships
Add following and followers pages

* Create :following and :followers actions in UsersController
* Restrict access to :following and :followers to signed in users
* Create :show_follow view to be rendered for either :following or
  :followers
Make the follow button work

* Create the Relationships controller
* Add create and destroy actions
* Restrict access to signed in users
Make follow button use Ajax

* Edit the follow/unfollow forms
* Arrange for Relationships controller to respond to Ajax requests
Add micropost feed

* Add the :from_users_followed_by method to the Micropost class. It
  should extract the ids of followed users and include them in a
  database query.
Reimplement the feed

* Reimplement the feed to use subselects and scale better