Remove lib/post-types.php and lib/metaboxes.php

We now recommend placing custom post types and
metaboxes within a plugin that contains all of
your site specific functionality.

See the latest update to https://github.com/retlehs/soil
to find an example:

https://github.com/retlehs/soil/tree/master/mu-plugins/base

functions.php

@@ -15,6 +15,4 @@ require_once locate_template('/lib/nav.php');             // Custom nav modifica
 require_once locate_template('/lib/htaccess.php');        // Rewrites for assets, H5BP .htaccess
 require_once locate_template('/lib/widgets.php');         // Sidebars and widgets
 require_once locate_template('/lib/scripts.php');         // Scripts and stylesheets
-require_once locate_template('/lib/post-types.php');      // Custom post types
-require_once locate_template('/lib/metaboxes.php');       // Custom metaboxes
 require_once locate_template('/lib/custom.php');          // Custom functions