Ignore disabled elements
Add support for adding event handler for form submit as well as a callback for invalidation on H5F setup.
Add minified version for the addition of the onSubmit and onInvalid handlers.
Document new onSubmit and onInvalid setup options on readme.
fix #45
support oninvalid
Merge pull request #52 from hax/master

Ignore disabled elements, event options

* Ignore disabled elements fix #45
* Add onSubmit and onInvalid options, fixes #51