Cleanup Scheduler at exit
Add timeout option for push registration
Base control conn readability on separate flag
Cleanup asyncore event loop on interpreter shutdown
Remove Cluster/Session.__del__
Use 0 instead of None for immediate scheduling
Avoid strong references between ControlConn and Connection
Make asyncore loop into a class, fix conn set usage
Wait for libev thread to terminate on exit
Avoid early termination of libev event loop
Merge branch '2.0' into del-and-daemon-thread-cleanup

Conflicts:
	cassandra/cluster.py
	cassandra/connection.py
	cassandra/io/asyncorereactor.py
	cassandra/io/libevreactor.py
Handle shutdown during schema agreement check