[81507580] minor formatting change to tariff updates' date

Add `tariff` formatting for `Time` objects. Uses `dd/mm/yyyy` allowing to copy & paste inside rollback *datepicker*.
Also add some parsing of times for `TariffUpdate` and `Rollback` models to keep all times in the same format.

[PT](https://www.pivotaltracker.com/story/show/81507580)
Merge pull request #36 from bitzesty/81507580-change-updates-date-format

[81507580] minor formatting change to tariff updates' date
Add MIT License
Docker setup
docker enhances

- use `macool/baseimage-rbenv-docker:latest` as base image to build docker image (based on phusion's baseimage)
enhances to run with `tariff-docker`

- Add a `backend_ip.sh` initialiser to container so it adds backend development ip *tariff-api.dev.gov.uk* to `/etc/hosts`
- `database.yml` will need to reference other `ENV` variables when linking containers from `tariff-docker`

For more info see [bitzesty/tariff-docker](https://github.com/bitzesty/tariff-docker)
enhance seeds

let's give default user all permissions so we don't get errors
specify port for backend
update crontab on startup.sh
reversing..
use sentry
better support of docker containers via ENV
install mysql-client when building docker container
add `docker` env

- use it by default on `startup.sh` (called by docker containers)
- copied from `production`, uses some caching and it's faster than `development`
- log this env's errors on sentry
- mock gds-sso authentication when running under `docker` env