support patch method

[kasperpeulen]

It seems like the PATCH method isn't supported:
http://restcookbook.com/HTTP%20Methods/patch/

This is used by firebase, would love to have this included in this package.

[nex3]

All methods are supported; you can create basically any kind of request you want using the new Request API. That said, it would probably make sense to add support for a patch() shortcut like we do for other common (and semi-common) methods.