Fixes error where app module cannot be imported

When calling `module()` with `inject()`, an error is thrown:
```
Error: [$injector:modulerr] Failed to instantiate module ng due to:
TypeError: 'undefined' is not an object (evaluating
'Function.prototype.bind.apply')
```

In karma-phantomjs-launcher 1.x, `Function.prototype.bind` isn't defined. Upgrading to 2.x
fixes this problem. In addition, it requires phantomjs-prebuilt as a
peer dependency.

(As an aside, the test was masking over the error. A more specific
error, or a message assertion would be better practice).

Author: kanhirun

package.json

@@ -27,10 +27,11 @@
     "karma-jasmine": "^0.3.6",
     "karma-jquery": "^0.1.0",
     "karma-mocha": "^0.1.8",
-    "karma-phantomjs-launcher": "^0.1.4",
+    "karma-phantomjs-launcher": "^1.0.0",
     "karma-sinon-chai": "^0.2.0",
     "karma-spec-reporter": "^0.0.18",
     "mocha": "^1.21.4",
+    "phantomjs-prebuilt": "^2.1.7",
     "run-sequence": "^1.0.2",
     "sinon": "^1.10.3",
     "sinon-chai": "^2.5.0"

test/unit/angular-zendesk-widget/zendeskWidgetSpec.js

@@ -8,7 +8,7 @@ describe('Angular Zendesk Widget', function() {
       module('zendeskWidget');
       expect(function() {
         inject()
-      }).toThrow();
+      }).toThrowError('Missing accountUrl. Please set in app config via ZendeskWidgetProvider');
     });
 
   });