Two dependencies bring in www/py-django so I have created two new slave ports which
use www/py-django16
* devel/py-django-tastypie-mongoengine allowed you to select django 1.6 or 1.8 in the options It now uses only 1.8
* add slave port devel/py-django16-tastypie-mongoengine which uses django 1.6
* www/py-django-tastypie now sets RUN_DEPENDS only if not already set
* add slave www/py-django16-tastypie which uses django 1.6
Approved by: mat (mentor)
Differential Revision: https://reviews.freebsd.org/D2913