Update therubyracer

0.10.2 has problems with Mavericks
Adding secret boolean field to songs
Ignore ctags files
Add a random string as the slug for secret songs

When the song is created as secret, the slug should be a random hex
string and not built from the title.
Rename Song#secret to Song#hidden

This way the opposite is `visible` and not `public` (which is a defined
method in Ruby).
Adding hidden and visible scopes to Song
Don't show hidden songs on user's timelines

User#recent_songs => User#public_recent_songs
Adding user#songs_visible_to(user)

This method will return the songs that another user can see. The
current user will be able to see all its songs, while only seeing the
visible songs of other users.
Test that timeline_songs shows my hidden songs but not others
Adding hidden checkbox to new song form
Merge pull request #8 from nhocki/secret_songs

Adding private songs.