Reorganise nav links.
Refactor variable names.
Rename parts of the styleguide nav to be BEM classic.
Add differing styles to the fixed page nav.
Edit text on the overview page.
Adjust nav height.
Refactor unstyled lists.
Use placeholder for unstyled nav element.
Merge branch 'master' into refactor/styleguide_navigation

Conflicts:
	app/assets/stylesheets/lib/_variables.scss
	app/assets/stylesheets/styleguide/_sg_navigation.scss
	app/assets/stylesheets/styleguide/_sg_variables.scss
Merge pull request #60 from moneyadviceservice/refactor/styleguide_navigation

Refactor style guide navigation with cleaner code and cleaner appearance.