Fix #12, correctly deregister hue control event listeners
Fix #12, correctly deregister hue control event listeners

Deregistering light state change event listener in hue control was done
incorrectly, so listeners would accumulate with every opening of the control
and after some use it would react to state changes of multiple lights.

Fixed by correctly deregistering last event listener before registering a new
one.

jtreml/home-command,jtreml/home-command