Please build artifacts for macosx-10.4-x86_64

As it stands, 10.8-intel won't work with most Twitter laptops, including mine, whereas 10.4-x86_64 should include everything we've had in the last four years.

See https://gist.github.com/wickman/5550908 for a bootstrapper script for rolling your own set of Python interpreters that build 10.4-x86_64.