Add tox and travis config file, update .gitnore.
First cut at a gevent connection class.

It seems to kind of work. The integration tests aren't working
right; that needs to be fixed before first. A simple test of the
basic functionality seems to work, but I've not yet tested the
recovery/retry and other execptional conditions.
Remove unused set.
Clean up.
Clean-up and refactor.
Use gevent as default connection class when monkey patched.
Bring back the timeout.
Small cleanup.
After re-preparing stmts, run query in executor

The query was being resubmitted on the event loop thread,
which could cause a deadlock if there were not any connections
available for use.
Log when connection creation is actually started
Raise min trash interval to 10 seconds
Check open conn count before submitting new creation task
Include open count in pool state string
Don't recommend using sudo + pip
Handle large messages through libev correctly

This fixes a problem similar to what 880408d92c2c5 fixed for
asyncore.
Merge pull request #51 from mattrobenolt/patch-1

Don't recommend using sudo + pip
Mark hosts up at the right time when adding them

Hosts outside of the intial set of contact points were not
being marked up correctly when they were discovered and added
to the cluster and sessions, resulting in them being skipped
for statement preparation and other operations.
Don't ignored libev conns closed by server

This bug was introduced by 31f684bb91f3e0a41238c869a7c8fc11ebf21515
Minor cleanup in metrics test
Define __str__ for Statement subclasses