test(ngClass): should initialize correctly when $observe and $watch have different initial values

This bug caused problems where ngClass was being used to identify whether a validation directive (such as required) was invalid,
where the ng-model was being initialized to a valid value before the first digest completed.
See this fiddle: http://jsfiddle.net/RobCannon/2AJCB/
fix(ngClass): should initialize correctly when $observe and $watch have different initial values

This bug caused problems where ngClass was being used to identify whether a validation directive (such as required) was invalid,
where the ng-model was being initialized to a valid value before the first digest completed.
See this fiddle: http://jsfiddle.net/RobCannon/2AJCB/