Compact lines

Ignore-this: 53b3295429be4c47c35440a704540157

darcs-hash:20130218113410-56b4d-a861d76a50a9d9edd991022d59ac1b19292452c3
Use classmethod decorator

Ignore-this: fdca2ce72b244a2f02719a0075c0bba3

darcs-hash:20130218115615-56b4d-d5c4e115d051b6e845c3e8b062f24f640499d024
Simplified code for cancelling remote SDP offers

Ignore-this: 113058752dfb51919d767eb4785024f8

darcs-hash:20130218131751-56b4d-61815e791fff7df26ed994bf58a127ede1896aeb