README
Install RSpec
Initial state of Bank
Bank#open sets the quantity of tellers
Change Bank::AlreadyOpen to Bank::InvalidStateError

It's more expressive and works for already closed banks.
Bank#close raises Bank::InvalidStateError
Bank#close sets the status of the Bank
Bank#initialize sets the quantity of tellers to zero
Document Bank::close
Prepare ground for Bank::Client
Install Virtus
Add the Bank::Client class
Bank has clients
Improve semantics in spec
Bank#add_clients_too_line respects state
Test adding clients to line
Document adding clients to line
Bank#add_client_to_line respects state
Install pry for debugging
Calculate waiting times