notification category filters

Summary:
Allows filtering notification by category. Category filters are also persisted in redux.

Adds a test suite for notification reducer

Reviewed By: passy

Differential Revision: D12999884

fbshipit-source-id: 5f8d2357e52f091c17b726e1f89ed68f3b7294fb

src/reducers/index.js

@@ -64,7 +64,7 @@ export default combineReducers({
     {
       key: 'notifications',
       storage,
-      whitelist: ['blacklistedPlugins'],
+      whitelist: ['blacklistedPlugins', 'blacklistedCategories'],
     },
     notifications,
   ),