style(playlist): rename files to match new format

public/app/features/playlist/all.js

@@ -1,5 +1,5 @@
 define([
-  './playlistsCtrl',
-  './playlistEditCtrl',
-  './playlistRoutes'
+  './playlists_ctrl',
+  './playlist_edit_ctrl',
+  './playlist_routes'
 ], function () {});