Keep track of your App's Market data

If you maintain any Apps in the Android Market then you have probably come across questions like

"How many downloads did the app have last week/month/year...?"

or

"Did the ratings improve since the last update?"

It's not easy to answer those questions since the Android Market's Developer console only gives you the current data. (There is statistics for active installs though.) So you have to keep track of these data yourself.
I found it quite tedious to do this by hand, so I built a little (Java) Selenium test that grabs the data and writes it to disk. Happily, it even runs headless, and can thus be easily put into the cloud. Lately, I fixed it up and put it on github. Hopefully this saves you some time, too.