Updating demo application to include Twitter/Password and support Firebase Login V2

@jdimond 

In this PR
1. Removed the dependency on `com.firebase:firebase-simple-login:*`
2. Updated the dependency on Firebase to `com.firebase:firebase-client-android:1.0.19-SNAPSHOT`
3. Added Twitter OAuth
4. Added Email/Password
5. Replaced all references to `simplelogin` to `login`