Bump rails from 5.1.3 to 5.1.4
Bump rails from 5.1.3 to 5.1.4

Bumps [rails](https://github.com/rails/rails) from 5.1.3 to 5.1.4.
- [Commits](https://github.com/rails/rails/compare/v5.1.3...v5.1.4)
ministryofjustice/prison-visits-public,ministryofjustice/prison-visits-public,ministryofjustice/prison-visits-public,ministryofjustice/prison-visits-public