app/assets/config/manifest.js
//= link_tree ../images
//= link_directory ../javascripts .js
//= link_directory ../stylesheets .css
//= link govuk-template.css
//= link govuk-template-ie6.css
//= link govuk-template-ie7.css
//= link govuk-template-ie8.css
//= link govuk-template-print.css
//= link fonts.css