Merge pull request #127 from aniversarioperu/master

Command t unfollow was incomplete
Replace be_true with be true
Replace be_false with be false
Replace be_nil with be nil
Corrected command to sort by last time tweeted

The current command includes ``--sort=tweets`` to sort users by last time the
users emitted a tweet. However, this parameter sorts by number of user's total tweets.
The correct parameter is ``--sort=tweeted``.