function _isSafari() {
    var n = window.navigator;
    return n.userAgent.indexOf('Safari') > -1 && n.userAgent.indexOf('Chrome') == -1;
  }
Same as the isIE(), but simply returns a boolean
THIS IS TERRIBLE AND IS ONLY USED BECAUSE FULLSCREEN IN SAFARI IS BORKED
If some other engine uses WebKit and has support for fullscreen they
probably wont get native fullscreen until Safari's fullscreen is fixed
@returns {Boolean} true if Safari