Improve documentation for login

[miguelasse]

Hey Luis,

Awesome library! I can't get the login class to work for me, when I try:

email = '[email protected]'
password = 'my_password'
my_utr = UTR(email, password)
my_utr.login()

I get this error:

ValidationError: 2 validation errors for Settings
email
  field required (type=value_error.missing)
password
  field required (type=value_error.missing)

Any thoughts on how to fix? I've been trying to login in a jupyter notebook and can't see how to pass my email / password appropriately based on the documentation.