Removes default version

Updates all AJAX requests to include api version
Requires namespaces to have version
Clean up code

assets/js/src/ajax.js

@@ -27,11 +27,6 @@ define('ajax', ['mailpoet', 'jquery', 'underscore'], function(MailPoet, jQuery,
         if(this.options.token === null) {
           this.options.token = window.mailpoet_token;
         }
-
-        // set default API version
-        if(this.options.api_version === null) {
-          this.options.api_version = window.mailpoet_api_version;
-        }
       },
       getParams: function() {
         return {