changing import in server.js to work with govuk-frontend module (#291)

server.js

@@ -220,7 +220,7 @@ function initialisePublic (app) {
   app.use('/public', express.static(path.join(__dirname, '/public')))
   app.use(
     '/',
-    express.static(path.join(__dirname, '/node_modules/govuk-frontend/govuk/'))
+    express.static(path.join(__dirname, '/node_modules/govuk-frontend/dist/govuk/'))
   )
 }