Changes to caolan/forms

Hello caolan

Thanks for your forms node module! I really like the shorthand way for creating forms quickly. I made a few changes to it that I hope you'll like:

* Added optional handlers for submit buttons and form method.

* Changed a string.replace() to a regex (for element id) so that it replaces more than just the first underscore when creating the label.

* Added documentation for the submit button.

Cheers!
vkareh