Bump up gevent requirement to >=1.0.
Cosmetic adjustments to make flake8 happy.
Merge pull request #92 from jpetazzo/gevent-1-0

Bump up gevent requirement to >=1.0.
Add flake8 to tox.
Add flake8 to Travis CI.
Merge pull request #93 from jpetazzo/jpetazzo/flake8

Add flake8.