Please update cffi to use master branch.

[Shinmera]

I've discussed this with @luismbo and it would be better if cffi was pulled from master instead of manual releases.

[quicklisp]

What's the canonical git home of cffi?

[quicklisp]

Never mind, found it on github. I'll update the source.

[phoe]

I think it is https://github.com/cffi/cffi - at least this is where I'm merging new commits into (as a freshly proclaimed CFFI co-maintainer).