fixes #55 (compiler warnings)
properly handle change responses that don't have an operation
remove FIXCATEGORYBUG interfaces since they're no longer needed (fixes #54)
reorganized unit tests
fixed willChangeObjectsForKeys: notification not firing
fixed a UI string being accessed across thread boundaries
fixed numerous compiler warnings on OSX
Retry if connection is reset by peer (fixes #57)
route all websocket sends through SPWebSocketManager
Added heartbeat to keep websocket alive