Updates Django 1.11 version in tox config
Updates Django 1.11 version in tox config

Django 1.11 officially released some time ago and a maintenance release
was even released soon after. The beta version reference is updated to
the standard semantic number scheme.

django-silk/silk,django-silk/silk,django-silk/silk,crunchr/silk,crunchr/silk,mtford90/silk,jazzband/silk,crunchr/silk,mtford90/silk,jazzband/silk,crunchr/silk,mtford90/silk,jazzband/silk,jazzband/silk,mtford90/silk,django-silk/silk