Remove py27-django19-grp TOXENV from .travis.yml
Remove py27-django19-grp TOXENV from .travis.yml

A bug in travis appears to be causing it to ignore this TOXENV, and so
it tries to run all tox tests, which inevitably times out.

sbussetti/django-nested-admin,sbussetti/django-nested-admin,sbussetti/django-nested-admin