Update to use pillar based configuration.

The redis configuration file is simple enough to make it purely
based on pillar data rather than a templated file.

This, whilst making the pillar data arguably more complex, does mean that
redis is now entirely configurable without needing to update this formula.
update CHANGELOG
pillar values have issues when using hyphen
Merge pull request #9 from ministryofjustice/pillar_based_config

Update to use pillar based configuration.