Fix language selector issue for files starting with de

When there is a file starting with de, the configuration defaulted the
lang value to de. This way, the multilingual implementation breaks. This
is fixed by properly specifying the path with a slash in the end.

_config.yml

@@ -49,7 +49,7 @@ defaults:
       lang:     "en"
   - 
     scope:
-      path:     "de"
+      path:     "de/"
     values:
       lang:     "de"
       hidden:   true