Added "scrollThen" that can apply a scroll animation before another transition

Related to issue #76

Usage:

  this.transition(
    this.fromRoute('posts'),
    this.toRoute('post'),
    this.use('scrollThen', 'toLeft'),
    this.reverse('scrollThen', 'toRight', {duration: 100})
  );
prefer an injection rule
we're not compatible with the latest beta at present
Merge remote-tracking branch 'origin/pr/105'
closes #112
adding scenario
Merge pull request #82 from jerel/master

Added "scrollThen" that can apply a scroll animation before transitions
Updating previous PR to match the new source organization
Merge branch 'master' into ember-1.9-compat
move away from deprecated form of #with