'Fills in and submits the login form.
Requires that the "login" form is visible.
This does NOT wait for the next page to load,
so the caller should wait for the next page
(or errors if that\'s the expected behavior).
Keyword Arguments:
email (unicode): The user\'s email address.
password (unicode): The user\'s password.'

def login(self, email='', password=''):

    self.wait_for_element_visibility('#login-email', 'Email    field    is    shown')
    self.q(css='#login-email').fill(email)
    self.q(css='#login-password').fill(password)
    self.q(css='.login-button').click()
