Fixes breaking change in Angular 1.3.0-rc0.

Returned values from directive controller constructors are now ignored, and only the constructed instance itself will be attached.

https://github.com/angular/angular.js/blob/master/CHANGELOG.md#since-1217-and-130-beta10
Variable Pane doesn't exists anymore.
Merge pull request #4 from gunta/master

Fixes breaking change in Angular 1.3.0-rc0.