tox env to easily run flake8

Most people know about pep8 which enforce coding style.  pyflakes goes a
step beyond by analyzing the code.

flake8 is basically a wrapper around both pep8 and pyflakes and comes
with some additional checks.  I find it very useful since you only need
to require one package to have a lot of code issues reported to you.

This patch provides a 'flake8' tox environement to easily install and
run the utility on the code base.  One simply has to:

 tox -eflake8

The env has been added to the default list of environement to have
flake8 run by default.

The repository in its current state does not pass checks but I noticed a
pull request fixing pep8 issues.  We can later easily ensure there is no
regression by adjusting Travis configuration to run this env.

More informations about flake8: https://pypi.python.org/pypi/flake8

1 files changed, 1 insertions, 0 deletions

diff --git a/test-requirements.txt b/test-requirements.txt
index 6da60814..116fbbd3 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,4 +1,5 @@
 # Remember to update README.md
 coverage
+flake8
 nose
 mock