Merge pull request #91 from Frique/ie7_support

IE7 support
Make shift-tab focus on the previous control

As it would when working with native form controls. Does not work in IE
yet, but so does regular tabbing at the moment.
Makes tabbing in/out of the control also work in IE

Follows tabindex attribute when using the tab / shift-tab keys through
the form.
Merge branch 'shift-tab' into frique-master