Add slug after the namespace, that makes more sense (#3274)

lib/plugins/graphite/data-generator.js

@@ -64,7 +64,7 @@ function keyPathFromMessage(message, options, includeQueryParams, alias) {
   }
 
   if (options.graphite && options.graphite.addSlugToKey) {
-    typeParts.splice(1, 0, options.slug);
+    typeParts.unshift(options.slug);
   }
 
   return typeParts.join('.');