Use Travis' pip cache config variable.
Use Travis' pip cache config variable.

spookylukey/django-debug-toolbar,spookylukey/django-debug-toolbar,django-debug-toolbar/django-debug-toolbar,pevzi/django-debug-toolbar,barseghyanartur/django-debug-toolbar,pevzi/django-debug-toolbar,barseghyanartur/django-debug-toolbar,tim-schilling/django-debug-toolbar,django-debug-toolbar/django-debug-toolbar,spookylukey/django-debug-toolbar,barseghyanartur/django-debug-toolbar,django-debug-toolbar/django-debug-toolbar,jazzband/django-debug-toolbar,tim-schilling/django-debug-toolbar,tim-schilling/django-debug-toolbar,jazzband/django-debug-toolbar,pevzi/django-debug-toolbar,jazzband/django-debug-toolbar