Add support for match -> unmatch transition, fix for #27

I always get this wrong, always forget that github creates an issue when you make a PR, so please forgive my incompetence here!

Anyway, this is a fix for the issue I raised previously, #27. Have tested in IE9 and can confirm it works a charm. If there are code style issues or anything let me know and I will endeavour to fix.

Cheers,
Nick