Add codesnippet for almost chronological order

Such as for downloading hashtag feeds, as discussed in #666 and contributed by
@e2tovar.

Also change comment color to grey in codesnippets in documentation.

docs/_static/instaloader.scss

@@ -36,7 +36,11 @@ code {
     color: #fff;
   }
 
-  .c1, .k, .kn, .ow {
+  .c1 {
+    color: #666;
+  }
+
+  .k, .kn, .ow {
     color: $color_instaloader_main
   }