add migrations and user associations

- users migration
- followings migration
- tweets migration
- retweets migration
- add models for above tables
- wire user associations for:
  - followiers
  - followed
  - tweets
  - retweeted_tweets
wire associations

- user followers followed associations
- tweets retweets
Merge pull request #1 from afayek1/setup

Setup
Merge pull request #2 from afayek1/status_updates

Views (user_home); Controller: Tweet
changed layouts. tweets post to index.