text: Title: authenticator.login() is takes too much time
  Body: Hi,
  
  First of all, thank you for writing this code.
  
  I have a problem though, which is that the authenticator.login() takes a bit too much time. When loading the streamlit page, it takes about 2 seconds to load the login form, which I think is a bit too slow.
  
  Writing this code, the time between print(3) and print(4) is really long.
  
  ```
  print(1)
  
  with open('config.yaml') as file:
      config = yaml.load(file, Loader=SafeLoader)
              
  print(2)
  
  authenticator = stauth.Authenticate(
      config['credentials'],
      config['cookie']['name'],
      config['cookie']['key'],
      config['cookie']['expiry_days'],
      config['pre-authorized']
  )
  
  print(3)
      
  authenticator.login()
  
  print(4)
  ```
  
  Hence, I would be able to speed up the authenticator.login() call. Is it possible?
  
  Thank you!
  