add factory for tweets
testing the order of a user's tweets
ordering tweets with default_scope. All tests pass.
testing that tweets are destroyed when users are
a user's tweets are destroyed along with the user
tests for Tweet model validations, length and empty tweet
add validations to Tweet model. Now, presence of content is required and max. length is 140 chars
Merge pull request #26 from danbender/tweetsters

Tweetsters