code: function (name, cb, lazy) {
              if (!lazy && name in triggerCache) {
                  cb(triggerCache[name]);
              } else {
                  singles[name] = singles[name] || [];
                  singles[name].push(cb);
              }
          }
docs: ## handler.one(name, callback, [lazy])
  Bind a callback to an event. Callback will run only
  once the next time the event is triggered.
  @param {string} name Event name.
  @param {function(?)} cb Event callback.
  @param {boolean} [lazy] True if this callback should not fire
  immediately if the event has already been triggered.