BSTabs.js: started on commenting. Not finished, though.

javascript/src/BSTabs.js

@@ -14,6 +14,8 @@ if (!QfqNS) {
     /**
      * Tab Constructor.
      *
+     * Programatically access Bootstrap nav-tabs.
+     *
      * @param {string} tabId HTML id of the element having `nav` and `nav-tabs` classes
      * @constructor
      */
@@ -34,7 +36,10 @@ if (!QfqNS) {
     };
 
     /**
-     * Get active tab from DOM
+     * Get active tab from DOM.
+     *
+     * Used upon object creation to fill the currentTab. It gets the ID of the currently shown tab. It does it, by
+     * targeting the element in the navigator having the `active` class set.
      *
      * @private
      */