swp_localization_init never fires

There is a bug in your l10n bootstrapping.

The file languages.php gets included on the plugins_loaded hook, but then uses the same hook to call swp_localization_init. Hence it will never be called.

Translations may still load in WordPress >= 4.6.0 but it will still circumvent the load_plugin_textdomain function and so prevent other plugins from hooking into the loading process.