title: How to find out if an email is already registered with Firebase Simple Login?
body: <p>I am using firebase (with Angularfire) for an html5 phone app. The user inputs only their email in the start screen, and then, depending on whether that email is already registered or not, the user is redirected to the login or registration page, respectively. For step1, how can we query the firebase simple login to determine if the email is registered or not?</p>