Change the app focus on login

I flipped the focus around on the login, before it would log you in and take you to the "Your Audience" screen to see your subscribers.

I've flipped this around to use the "Newsletters" screen instead, not 100% sold on this being better. But I do think it helps the users flow through the app and makes more sense.

I swapped the menu options around on the nav bar too so "Newsletters" comes first.