Added Tweeted field to post model.

Validations also added for presence and for true/false only.
Factorygirl was updated as well (without update, all tests will fail.)
Scope of notTweeted was also added for rake task to be built.
Added unit tests for post model to ensure :tweeted behaves as expected

Can only be true/false
defaults to false
Is not blank.
Added tweet_untweeted method.

Not quite working yet. Proof of Concept.
Made tweet_untweeted a live method that will update to twitter.

Moved from controller to method.
Also required a save, otherwise the tweeted field wouldn't change.
Generate tweet rake task.

Take will call Post.tweet_untweeted and twitter will work its magic.
Had to make a dependency => :environment
Merge branch 'twitter'

Conflicts were fixed and non-issues.