Transfer the cookie-signature npm package to the organization #533

I'm opening this because we discussed transferring the cookie-signature npm package to the organization a long time ago: tj/node-cookie-signature#36

I'm happy to be the captain if you're looking for someone.

We haven't been able to transfer the repository because TJ is hard to reach, but if anyone can get in touch with him, that would be great. Having the npm package under the organization is more than enough, though.