#124/get items by group (#147)

* Add getItemsByGroup function

* Update test

* update readme

* Update README for submit button

* Update docs with ID prop for button and submit components

src/scripts/lib/clay-config.js

@@ -182,6 +182,17 @@ function ClayConfig(settings, config, $rootContainer, meta) {
     });
   };
 
+  /**
+   * @param {string} group
+   * @returns {Array.<ClayItem>}
+   */
+  self.getItemsByGroup = function(group) {
+    _checkBuilt('getItemsByGroup');
+    return _items.filter(function(item) {
+      return item.config.group === group;
+    });
+  };
+
   /**
    * @returns {Object}
    */