added accessibility enhancements for details element
fixed js to detect if open close state
swapped append and attr method calls, removed aria-expanded attr on panel
Update details/summary polyfill

- Set aria-controls, aria-expanded and aria-hidden attributes
- Check to see if details has open attribute and update aria attributes
- Add open attribute to test at /examples/details-summary
Set and update aria-hidden attribute
Remove console.log
Add a secondary heading style for large headings
Use heading mixin for secondary heading style to increase spacing between secondary and main headings
Improve readability and adjust whitespace

Update check to see if detailsAttr is undefined
- Improve readability, as typeof undefined will always result in the
string 'undefined'

- Adjust whitespace
Merge branch with master.
Merge pull request #28 from alphagov/aria-for-details-summary-test

ARIA attributes for details summary polyfill
Merge pull request #26 from alphagov/adjust_secondary_headings

Looks sensible to me. Thanks Tim!
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
Move pattern test pages

- Move individual patterns to /patterns/ to show test pages
- Update routes.js
Change styling suggestion for validation

Having a red background can cause issues with the contrast ratio of validation text.
Merge pull request #32 from alphagov/change-validation-styling-advice

Change styling suggestion for validation
Merge pull request #31 from alphagov/move-details-summary-to-patterns

Move pattern test pages