Fix missing on and off labels, add knob-labels, plus tests.

Ok, let's try again.  This should be clean.  Forked from your master.

Changes:

1) Added `.bowerrc`.  Bower was not using the correct directory on my machine because a `.bowerrc` file was found in a parent directory.
2) Fixed issue when labels were not specified by using `attr.` instead of `$scope.`.
3) Added tests for default labels.
4) Added knobLabel and tests.