assisted digital updates

- fixed video
- inserted correct links
- slight updates to content
Remove unused layout
Merge pull request #353 from alphagov/assisted-digital-changes-

assisted digital updates
Add colorize gem to use the links.rb tool
Remove unused Sass files relating to old design patterns content
Update to reflect 301 responses
Fix broken link in breadcrumb
/users now redirects to /user-centred-design

Don’t make the web slower than it needs to be.
Create design pattern page layout and styles
Remove unused page status styles
Reduce margin of page headers
Add pattern example container styles
Add design pattern guides and example images
Merge branch 'master' into add-section-on-design-patterns
Content updates and corrections following review with team
Create 'GOV.UK Elements' landing page

This page links to the alpha version of the GOV.UK Elements.

It's included here  so that searching the Service Manual for things like 'colour' will return a result.
Delete obsolete guides and update or remove links to them

See this spreadsheet for details of what redirects we'll need: http://goo.gl/QYgkES
Delete unused pattern example images
Consistent punctuation around etc

See alphagov/design-principles#164
Remove direct links to heroku and explain alpha status of elements page