this issue fixes #413

connections that have gotten a mismatch number of responses to requests in a pipeline should be disconnected
ConnectionPools in forked and multi-threaded environments play nicer.

Thanks Christian Joergensen. Fixes #412
Merge branch 'master' of github.com:andymccurdy/redis-py
version bump to 2.9.0
remove pytest's cache directory and *.pyc files from distribution
Merge pull request #414 from shearic/fix_badconnection

this issue fixes #413