Change application.css to not pull in all CSS in the tree, as the active_admin CSS (which is quite large) was being complied into the non-admin CSS. active_admin expects active_admin.css.scss to be in /app/assets/stylesheets (and only there, no subdirectories).

To fix this, I moved all app-specific CSS into an 'app' subdirectory of 'stylesheets' and changed application.css to pull everything from that directory (and only that directory).