title: Search information by user on firebase
body: <p>This is probably very simple ,so sorry... 
  I'm trying to create an application where i can create users and store informations by Firebase. There is an example here :</p>
  
  <p><a href="http://image.noelshack.com/fichiers/2015/11/1426182307-log.png" rel="nofollow noreferrer">http://image.noelshack.com/fichiers/2015/11/1426182307-log.png</a></p>
  
  <p>But now I want to check if the name already exists if someone wants to create a new user.</p>
  
  <p>How would I go about grabbing individual user information without knowing their id , like simplelogin:54?</p>
  
  <p>I've found this topic <a href="https://stackoverflow.com/questions/14963776/get-users-by-name-property-using-firebase">Get users by name property using Firebase</a> but it is not the same thing because in my case I don't know the children after "Users"</p>
  
  <p>Cheers,</p>