Automated regression testing

We need to set up some kind of performance regression testing.

@rrnewton and I started to set this up at http://codespeed.crest.iu.edu, following @nomeata's example for ghc at http://ghcspeed-nomeata.rhcloud.com, but so far we haven't managed to get it to work. We are not pythonistas though, so if anybody wants to volunteer to help, and perhaps sway my opinion of untyped languages in the process, please do.

I'll leave this open to remind us to sort it out.