Merge pull request #11 from zagadooga/Austin

Austin
added author_id column to tweets table, updated create new tweet to populate this with the tweet author
Implemented followers button and unfollow feature.
Merge pull request #13 from zagadooga/followers_page

Implemented followers button and unfollow feature.
fixing merge conflicts on index page, controller
Merge pull request #14 from zagadooga/dannyg

Dannyg
merge
merged with master
Update README.md
done with retweet functionality
Merge branch 'master' into Austin