respond to subscription even if "nothing changed"
respond to subscription even if "nothing changed"

fixes #320

belisarius222/arvo,ngzax/urbit,urbit/urbit,cgyarvin/arvo,ngzax/urbit,cgyarvin/arvo,jfranklin9000/urbit,urbit/urbit,eglaysher/arvo,jfranklin9000/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,ngzax/urbit,belisarius222/arvo,jfranklin9000/urbit,urbit/urbit,ohAitch/arvo,jfranklin9000/urbit,urbit/urbit,solri/arvo,ohAitch/arvo,ngzax/urbit,joemfb/arvo,jfranklin9000/urbit,urbit/urbit,Fang-/arvo,urbit/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,joemfb/arvo