Add simple cron script to run hourly.

Ooops, looks like you accepted the previous pull request for this, but then it got lost when merging my other branch (that's my fault for the sloppy commit history; I started with a branch that had this file, and then I dropped it when rebasing back on your master branch, then when you merged my branch it dropped this file again. 

Anyway, here it is again, same as last time.