Fix alignments for exturl with mobile_layout_economy option. (theme-next#411)

* Fix alignments for `exturl` and footer with `mobile_layout_economy` option.

* Remove footer alignment.

Author: ivan-nginx

source/css/_common/scaffolding/mobile.styl

@@ -76,6 +76,11 @@
       padding: 0 18px;
     }
 
+    // For external links alignment.
+    > span.exturl {
+      margin-left: 18px;
+    }
+
     // Rewrite paddings & margins inside tags.
     .note > p, .tabs .tab-content .tab-pane > p {
       padding: 0 5px;