add precommit tox env, pypy-dj19 and pypy3-dj19 to travis
add precommit tox env, pypy-dj19 and pypy3-dj19 to travis

kevgathuku/django-extensions,haakenlid/django-extensions,kevgathuku/django-extensions,linuxmaniac/django-extensions,django-extensions/django-extensions,kevgathuku/django-extensions,linuxmaniac/django-extensions,django-extensions/django-extensions,haakenlid/django-extensions,haakenlid/django-extensions,linuxmaniac/django-extensions,django-extensions/django-extensions