Update middleware to support Django 1.10

[grschafer]

Updates the middleware to be django 1.10-compatible as suggested here: https://github.com/selwin/django-user_agents/issues/13

Updates some out-of-date settings, imports, etc so that tests are runnable.

• Templates: https://docs.djangoproject.com/ja/1.9/ref/templates/upgrading/
• URL patterns: https://docs.djangoproject.com/en/1.9/ref/urls/#patterns
• TestCase class: https://docs.djangoproject.com/en/1.10/topics/testing/tools/#simpletestcase

[grschafer]

Updated travis CI matrix based on django release notes on python compatibility:

[selwin]

Thanks!