fix(scenario-runner): support data-ng and x-ng based attributes

Prefixed attributes like data-ng-model and x-ng-model were not being
found by the Selector. It was only looking at ng: and ng- prefixed
attributes.
Added a few tests as well to ensure the aforementioned prefixed
attributes are being matched properly.

Closes #1020

src/ngScenario/SpecRunner.js

@@ -119,7 +119,9 @@ angular.scenario.SpecRunner.prototype.addFutureAction = function(name, behavior,
         });
         var result = $document.find(selector);
         if (selector.match(NG)) {
-          result = result.add(selector.replace(NG, '[ng-'), $document);
+          angular.forEach(['[ng-','[data-ng-','[x-ng-'], function(value, index){
+            result = result.add(selector.replace(NG, value), $document);
+          });
         }
         if (!result.length) {
           throw {