Add linting to travis CI.
Add linting to travis CI.

marcgibbons/django-rest-swagger,marcgibbons/django-rest-swagger,marcgibbons/django-rest-swagger,pombredanne/django-rest-swagger,pombredanne/django-rest-swagger,pombredanne/django-rest-swagger,marcgibbons/django-rest-swagger,pombredanne/django-rest-swagger