docs(toh-6): systemjs.config.json -> systemjs.config.js (#2116)

Copyedit in file tree.

Author: chalin

public/docs/ts/latest/tutorial/toh-pt6.jade

@@ -568,7 +568,7 @@ block filetree
       .file index.html
       .file package.json
       .file styles.css
-      .file systemjs.config.json
+      .file systemjs.config.js
       .file tsconfig.json
       .file typings.json