Update swapClass method

Simplifies swapClass method using jQuery removeClass().addClass()
chaining to fix issue where swapped classes merge into classes already
present, e.g. is-activenav-tasks’.
Merge pull request #101 from moneyadviceservice/fix/mas-collapsible

Update swapClass method
Make the skip to content link stand out more
Merge pull request #110 from moneyadviceservice/fix_skip_to_main_content_link

Make the skip to content link stand out more
Adjust type and heading placeholders
Adjust component type sizes
Add h4 headings to guide example page
Remove type sizes from list icons
Adjust heading sizes
Revert heading levels to represent CMS output
Remove redundant intro section with image
Change base font size to 19 and line height to 1.4
Merge branch 'new_body_font_and_weights'
Update mock categories response in line with the public_website API

See: https://github.com/moneyadviceservice/public_website/commit/1ba599d980df85870cd2fd2233eb7675ca30108b
Use updated attributes with category reader and entity
Merge branch 'master' into category_page_level_one
Add classes to align the columns in IE8