Let Travis run against MySQL and Postgres
Let Travis run against MySQL and Postgres

And to finish it off, I'm updating Travis configuration to also run
pytest with the new environment variables to set different database
backends.

skirsdeda/django-treebeard,skirsdeda/django-treebeard,skirsdeda/django-treebeard,django-treebeard/django-treebeard,tabo/django-treebeard,skirsdeda/django-treebeard,tabo/django-treebeard,django-treebeard/django-treebeard,tabo/django-treebeard,tabo/django-treebeard,django-treebeard/django-treebeard