Add an interval to remove expired follos
follo: if a new user joined, we refresh the whole follo to retrieve the new user's data
follos : saved in a map instead of an array
follo: remove the loading div (useless now)
follo: update the current follo is the global list has been refreshed
follos invite: change the prompt (the old one was deprecated)
follos prompt invite: check if user is not invited to this follo first 
code enter uppercased
follo list user map: increase the height