Fixed Cython version dependency check

Ignore-this: 1590a79188e56ba8b25e551e0d41066c

darcs-hash:20131213130301-56b4d-e79065b3d425b6a9951c00b490d24fb47b238050
Avoid exceptions in IncomingSubscription.end

Ignore-this: 20ecc3f78773687572fc5be1297b2a09

darcs-hash:20131223122810-56b4d-46eb0d35624a22cc0047414c37f8b17e7b808297