Allow for a jQuery-style custom data hash to be passed to the event listening functions

In order to use Zepto with [sudo.js](https://github.com/taskrabbit/sudojs) the jQuery style custom-data-hash-for-events needs to be supported. I found the previous PR for this feature but, given the time-lapse, felt it better to submit a fresh one with what is perhaps a better stylistic fit.

All tests pass and a few have been added to both event.html as well as zepto.html