I have just build the App. It is in the AppStore and it is called B.L.A.F., you can simply type blaf into the search, please, have a look at its log in and registration systems. It is exactly what YOU NEED. It uses [login to view URL] to serve In-System Log In and Sign Up processes, as well as I've built in Facebook Log In, which creates account on the parse and links it to the System. Also it takes all necessary info from Facebook as Image, name, email, gender, age.
I think I will be the best candidate, because I have the exact experience you are looking for, and I did it just couple weeks ago, which gives me an opportunity to make it twice as fast than almost anybody else.