Use jest to mock electron in tests

Summary:
Replacing our custom electron-stubs transform with a mocked module.

This will now be the default impl for tests, and we can override it by mocking as needed.

Reviewed By: passy

Differential Revision: D17979659

fbshipit-source-id: a26994158d439fa7dc1ca38225294106fc4e1559

src/__tests__/server.device.tsx

@@ -7,6 +7,13 @@
  * @format
  */
 
+jest.mock('../fb-stubs/Logger');
+try {
+  jest.mock('../fb/Logger');
+} catch {
+  // Allowed to fail when fb modules are not present.
+}
+
 import Server from '../server';
 import {init as initLogger} from '../fb-stubs/Logger';
 import reducers, {Store} from '../reducers/index';