add footerViewClass to Bootstrap.ModalPane so footer may be easily extended
added modal pane footerViewClass test
Merge remote-tracking branch 'upstream/master'
Merge pull request #72 from arenoir/master

Add footerViewClass to Bootstrap.ModalPane
Merge remote-tracking branch 'upstream/master'

Conflicts:
	packages/ember-bootstrap/lib/views/modal_pane.js