Basic support for Gfycat

While Gfycat does have an oembed endpoint (
http://gfycat.com/cajax/oembed/:id) it doesn't return any information, just an iframe in the html element (http://www.reddit.com/r/gfycat/comments/2kq4da/bug_gfycats_oembed_does_not_work_at_all/)

I hope to someday rewrite this provider to use http://gfycat.com/api to provide some more useful information and tighter integration.