Migrate to Django > 1.9

Erase dependency from djorm-pgarray and utilization of the native PostgreSQL support of array objects through: django.contrib.postgres

Release 1.8 will be stable around mid-April (https://code.djangoproject.com/wiki/Version1.8Roadmap) and, until then, the dependency on the djorm-pgarray library will have to be preserved.

Current release is 1.9 as of Februrary 2016.
