Fix ParseFacebookUtils uninitialized exceptions.

Repro steps:
1. Log in to the app.
2. Close the app.
3. Reopen.

- Add ParseFacebookUtils.init() in Application.
 * In LoginActivity.onCreate(), UserDetailsActivity is shown right
 after the user has logged in.
 * If user has logged in and then closed the app, the app will crash
 after the user reopen the app since ParseFacebookUtils is not inited
 in the code path.