Fix doc + use hasOwnProperty

Author: Vadorequest

src/ng/controller.js

@@ -30,10 +30,10 @@ function $ControllerProvider() {
   /**
    * @ngdoc method
    * @name $controllerProvider#has
-   * @param (string) name Controller name to check.
+   * @param {string} name Controller name to check.
    */
   this.has = function(name){
-    return (name && controllers[name])? true : false;
+    return controllers.hasOwnProperty(name);
   };
 
   /**