www/py-django-mezzanine: Fix run dependency versions

Loosen the dependencies listed in setup.py:install_requires so that
port dependencies can satisfy them. This fixes run-time errors such as:

pkg_resources.DistributionNotFound: The 'future==0.9.0' distribution was not found and is required by Mezzanine

• Update and sort RUN_DEPENDS, remove chardet
• Add TEST_DEPENDS
• Rename test target now that framework supports TEST_DEPENDS et al.
• Update test target to set some environment variables that if not set can cause test failures in particular environments.

PR: 200994
MFH: 2015Q4