Watch `ng-options`, Don't copy `ng` classes from select element

[nycitt]

Fixed 2 issues I had:

1. Whenever changing the contents of the options (via ngOptions) the bootstrap-select element doesn't update [http://stackoverflow.com/questions/34183390/how-can-i-write-an-angular-directive-to-listen-to-changes-in-ngoptions](StackOverflow problem)
2. The ng- classes keep getting copied over when doing a refresh. We don't want that to happen (ex: copies ng-validation)