Merge pull request #1544 from matrix-org/luke/groups-store-add-unregister-api

Add unregiseterListener to GroupStore

src/stores/GroupStore.js

@@ -92,6 +92,10 @@ export default class GroupStore extends EventEmitter {
         this._fetchMembers();
     }
 
+    unregisterListener(fn) {
+        this.removeListener('update', fn);
+    }
+
     getSummary() {
         return this._summary;
     }