Trigger method optimizations

This pr adds a special internal function
```js
Marionette._triggerMethod
```

How should I benchmark this. The only benchmark I've used so far is the reported running time of the test-suite. According to `mocha` post these changes the tests run `30ms - 40ms` faster (with a couple extra tests). Note: `triggerMethod` is called 7790 times in the specs

Feel free to reject as this really dirties the code, but I feel it may be worth it for such a hot function