patch on hashchange function to only run if hashchange option is true

I patched the on 'hashchange' function to only run if the ```hashchange``` option is set to ```true```

I was getting console.log errors when I integrated [jquery.address](https://github.com/asual/jquery-address) (which uses hashchange), despite the hashchange option set to false. This was because an ```.on()``` event was binded to ```hashchange``` (regardless of the option setting) in the ```src/setup.js``` file.