Add unique screen name index to tweeters table
Change some Tweeter method names and update docs

* Tweeter#most_favorite_tweeters -> calculate_most_faved
* Tweeter#most_retweeted_tweeters -> calculate_most_retweeted
* Tweeter.favorite_tweeter -> calculate_favorite_tweeter
Make favorite tweeter a hash

* Remove attr_accessor stuff from Tweeter model
Move all stat calculation into Tweeter model

* This commit won't work because the attributes aren't created yet
Add stat columns to tweeters table

* Add serialized attributes for stat columns to Tweeter model
Add resque gem
Use dotenv-rails gem instead of dotenv
Add Resque rake tasks

* Get Resque's redis working locally
Remove gitkeep from lib/tasks
Add stats_job_queued_at column to tweeters table
Move stat calculation to resque job
Loosen auth requirements for Tweeter#show

* Only require auth if the tweeter's stats have never been calculated
  and aren't currently being calculated
Add AJAX polling for stats calculation

* Add TweetersController#stats endpoint for AJAX poller
Merge pull request #7 from jakeboxer/resque

Do stat calculations in a Resque job