Fix pyflakes errors.
Add custom pyflaks runner.
Merge branch 'master' into 67-pyflakes-clean
Update travis to run twistedchecker.
Check twistedchecker with pyflakes.
Update pip to pin versions from install_requires
Merge pull request #74 from chevah/67-pyflakes-clean

Clean code of pyflakes warnings
Revert verstion.
Merge master.