Environment Based Security Token

`config.secret_key_base` relied on `RAILS_SECRET_TOKEN` being set in all environments. Since development and (especially) test environments are not guaranteed to have `RAILS_SECRET_TOKEN` set, a check was added for these environments to use a default value. Production will continue to **raise an error** when the environment variable is unset.

My build was still failing after the fix since the migrations were not being run. Migrations are now run as part of _prepare_ in `dciy.toml`.