function _ready() {
         if (!document.body) {
            return window.setTimeout(_ready, 50);
         }
         getImageProgress = gamejs.image.preload(RESOURCES);
         try {
            getMixerProgress = gamejs.audio.preload(RESOURCES);
         } catch (e) {
            gamejs.debug('Error loading audio files ', e);
         }
         window.setTimeout(_readyResources, 50);
      }
ReadyFn is called once all modules and assets are loaded.
@param {Function} callbackFunction the function to be called once gamejs finished loading
@name ready