Remove bottom margin, as this is already set on the surrounding form-group
Update naming of date styles so they're not specific to date-of-birth
Pattern page to test form date

- Create test page with a single pattern
- Update routes.js
Merge pull request #30 from alphagov/improve-date-of-birth-pattern

- Change .date-of-birth classname to .form-date
- Remove bottom margin on .form-group within .form-date
- Add a test page at /patterns/form-date