Update newsletter subscription heading to H2
Merge branch 'email-headingd-fix'
Add skip to main link to the styleguide pages
Merge pull request #518 from moneyadviceservice/fix/skip-to-main-nav

Add skip to main link to the styleguide pages
Add GB suffix to alternate metatags
Merge branch 'bug/alternates-sufix'
Use HTTPS map image to avoid security warning
Prepare the category tree on application init
Merge branch 'warmup-category-cache-on-init'
Only warm category cache when rails server is being started
Don't escape contents on news index page
Filter flash to only display info, success and error messages.

Avoid displaying [flash commands](https://github.com/moneyadviceservice/public_website/blob/master/app/controllers/commands/command_helper.rb) set by the public website.