protected_branches_controller.rb

1. Modify the component to support a callback for every key press in the
   filter. We need this so we can update the "Create: <branch_name"
   label.

2. Modify the component to use `$(<selector>).first().click()` instead
   of `$(selector)[0].click()`, because the latter is non-standard, and
   doesn't work in PhantomJS.