Wait to do the form DOM scans until absolutely necessary
Add support for `data-confirm` attribute on `button` elements.

This should be supported as the `button_to` rails helper produces
the expected `data-*` attributes.

Closes #352.
Merge pull request #336 from MoonScript/speed-up-form-novalidate

Speed up submit for [novalidate] and [data-remote!=true] forms
Merge branch 'master' into data-disable
Update replacement logic to avoid DOM operations when we won't change the HTML after all.