Updates to forms chapter.
Updates to forms chapter.

- Changed RepHtml to Html
- switched <input type=submit> to <button>Submit (consistency)

maxigit/yesodweb.com-content,wolftune/yesodweb.com-content,wolftune/yesodweb.com-content,maxigit/yesodweb.com-content,mlitchard/lambdaweb.com-content