HTML5 form plugin, validation constraints & WAI-ARIA/accessibility

Hi Adell,

Please pull (see bug #84):

 * Added a Javascript plugin: `contributed/jquery.jeditable.html5.js`
 * Added tests: `tests/index.html`
 * Added a demo page: `html5.html'

Additional supported types (so far):
 * "html5_text" (`<input type=text >`), "number", "email", "url".

Additional configuration properties:
 * inputmode, list, maxlength, pattern, required, min, max, step, html5_placeholder, html5_error_text.


Many thanks, Nick