Various changes to accomodate running tests (including integration tests)
on a vagrant installation. Includes detection of TESTING environment in
settings.py. Raising of deis user permissions in provisioner to allow
test DB creation. Extending test setup to use installations with
existing superuser. Updating docs to desribe testing procedures.

Amend Travis config to create the testing DB with the 'deis' role

Add 'vagrant' to PROVIDER_MODULES in settings.py to ensure consistency with local_settings.py. And therefore increase falvors count in tests. Also updated DATABASE dict to not use a password in testing env.

Get travis to create databse with name 'deis', not 'deis_testing'

Create deis postgres role before creating DB in travis.yml

Don't surround psql commands in double quotes in travis.yml

Resort to switching postgres role and db name depending on testing env

Flake error for line length