FIX: You can't change a subject whilst Flagging

Meta: [You can't change a subject whilst Flagging](http://meta.discourse.org/t/you-can-t-change-a-subject-whilst-flagging/6887)

This revert a change made by @eviltrout in b794830a259d0c76bf804227ab2653b4f9118eb6 in the `flag_view.js`.
The `Em.run.schedule('afterRender', function() {...})` is apparently not enough. Had to schedule the event on the next run loop.

Hopefully, the PR emberjs/ember.js#1235 will soon be merged in and we'll have a proper radio button control in Ember.js.
Merge pull request #907 from ZogStriP/fix-you-cant-change-a-subject-whilst-flagging

FIX: You can't change a subject whilst Flagging