Prevent control bar from attatching event listeners when disabled. Fixes #556

Issue #556, Reproduce: http://jsbin.com/ikewix/3/edit

This commit refactors how videojs handles the control options, ie: {controls: true} and {controls: false}. The biggest change is that the ControlBar no longer attaches its event listeners if has been disabled through the options. 

I think this change makes sense since the ControlBar doesn't need the event listeners if it's disabled. It might affect anyone trying to reenable after init has been called, but this doesn't seem like it's a common use case.