Travis: allow doc warnings until docs review is complete

Once #3307 is complete this should be dropped.
Makefile: add pep8 command
Travis: bump Django to 1.6.5 add 1.7.1

Allow Django 1.7.1 to fail as it wants Django migrations and not South
migrations.
Travis: disable migration testing

Bring this back once we have a migration path from older versions.
Travis: force MyISAM

At least until we close #3363 and #3364
requirements: reminder to drop argparse
setup: install_requires can process --allow-external and --allow-unverified
Logging: add default log directory
requirements: importlib on Py < 2.7
Travis: disable install testing
Travis: enable py.test testing
Tests: use pytest-django < 2.7
Travis: hard dependency on Redis
requirements: let travis.txt pull in test requirements
Travis: don't test against PG and sqlite

Since MyISAM is hardcoded we will fail against these databases for now.
Travis: drop memcached
Travis: use Dummy cache for testing