bind the proxy events to the current app.
function() {
      var proxy = this, app = this.app;
      $(window).bind('hashchange.' + this.app.eventNamespace(), function(e, non_native) {
        // if we receive a native hash change event, set the proxy accordingly
        // and stop polling
        if (proxy.is_native === false && !non_native) {
          Sammy.log('native hash change exists, using');
          proxy.is_native = true;
          window.clearInterval(Sammy.HashLocationProxy._interval);
        }
        app.trigger('location-changed');
      });
      if (!Sammy.HashLocationProxy._bindings) {
        Sammy.HashLocationProxy._bindings = 0;
      }
      Sammy.HashLocationProxy._bindings++;
    }