Use Basic Auth and pass cookies (for master)

Here's a bare version atop the current master which solves the "Cookies must be enabled to use GitHub." problem.

It does so by switching from Token auth to Basic Auth, and using a cookie jar in .git/cookie-jar.

Feel free to close one of these if you merge the other - I don't know what your plans are for the next release, nor whether the commits on your master are intended for release shortly.