Update php/JFormComponentHtml.php

Added required "extends JFormComponent" 
Form 'action' fix for non-canonical document roots

The 'action' attribute on jFormer forms is correctly determined when
the website's document root is a non-canonical path, e.g. a symlink.
Merge pull request #14 from Hamled/action_path_fix

Form 'action' fix for non-canonical document roots
Merge pull request #13 from adelmazza/master

JFormComponentHtml bug fix

Thanks!