Make sure footer columns don't stack on smaller screen sizes

app/views/layouts/_footer.html.slim

@@ -1,12 +1,12 @@
 footer
   .container
     .row
-      .col-md-6
+      .col-md-6.col-xs-6
         ul.links
           li = link_to 'About', about_path
           li = link_to 'Terms of Service', tos_path
           li = link_to 'Privacy Policy', privacy_path
 
-      .col-md-6.text-right
+      .col-md-6.col-xs-6.text-right
         ' Developed with passion by
         = link_to 'Marcin Kulik', 'https://github.com/sickill'