Update rx for #61

This is a cursory upgrade and could be taken further. The tests all
pass, but I want to make sure this really works before cleaning up
further.
Merge branch 'upgrade-rx' of github.com:daveray/PigPen into daveray-upgrade-rx
Update more code to use rx bindings. Remove *max-load-records*!
Clean up unsubscription
Merge pull request #77 from Netflix/upgrade-rx

Upgrade rx