fix(docs.js): handle empty deps array for plunkr/jsfiddle

Change return value of docsApp.serviceFactory.prepareDefaultAppModule
to include empty array `[]` instead of array containing one empty
string element `['']`.

This will correct script.js for simple plunkr/jsfiddle examples such
as [ngChecked](http://docs.angularjs.org/api/ng.directive:ngChecked).

docs/src/templates/js/docs.js

@@ -359,7 +359,8 @@ docsApp.serviceFactory.prepareDefaultAppModule = function() {
     var moduleName = 'App';
     return {
       module : moduleName,
-      script : "angular.module('" + moduleName + "', ['" + deps.join("','") + "']);\n\n"
+      script : "angular.module('" + moduleName + "', [" + 
+          (deps.length ? "'" + deps.join("','") + "'" : "") + "]);\n\n"
     };
   };
 };