Took a stab at format on save functionality

This may work for formatting on save, which would be a nice feature to have.
Update format.coffee
Update format.coffee
Somewhat working format on save
Format on save for every js file if setting is true
Make activation events array empty so package's activate method runs when Atom opens.
Format on save now works :)
Created observer for format_on_save
Only formats on save now, setting can be changed at anytime

Method called to handle all subscriptions
Merge pull request #17 from ilanbiala/patch-1

Format on save