added postgresql and mysqldatabases for django 1.6, 1.5 and 1.4 to travis.yml
added postgresql and mysqldatabases for django 1.6, 1.5 and 1.4 to travis.yml

HowGood/django-bulk-update,torchingloom/django-bulk-update,aykut/django-bulk-update,lead-ratings/django-bulk-update