Allow heading tag helper to accept optional attrs
Allow heading tag helper to accept optional block
Apply accessible headings to views
Add accessible headings to the content
ActionPlanDecorator is a ContentItemDecorator

Allows ActionPlanDecorator to inherit the default html_processors that are common for all the content decorators
ActionPlanDecorator keeps the right aria-level value
NewsArticleDecorator uses the inherit html processors
Merge pull request #597 from moneyadviceservice/headings

Accessible Headings