Tagedit's forward-slurp-tag *almost* works in web-mode

Some of the outer tag's formatting still gets horked, but the core of
it is working now.
tagedit-forward-slurp-tag works in web-mode

I had to hack tagedit to do it. My current hack may not be very robust,
but when I'm finished hacking on this I'll have to run that by the maintainer.