Removed flake8 from travis config.
Removed flake8 from travis config.

Flake errors shouldn't break the build, especially since flake8 complains
at autogenerated code (migrations) which we don't want to fix, and it
often has false positives with other code. These should be considered
warnings, not errors.

ryanshawty/django-mailer,pinax/django-mailer,felixxm/django-mailer,jawed123/django-mailer,chriscauley/django-mailer,Ubiwhere/django-mailer,temnoregg/django-mailer,pinax/django-mailer,spookylukey/django-mailer