Fix typo that was preventing Binding.stop() from working.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)
Merge pull request #458 from enyojs/binding-stop-typo-fix-graynorton

Fix typo that was preventing Binding.stop() from working.

Reviewed-By: Ben Combee (ben.combee@lge.com)