Add tests under accounts with different permissions

[aldarund]

Need more tests using credentials for customer admin, reseller admin and email account user.
Api key for all this entities can be obtained during test via regenerate_api_key method. See here #20
Tests should include attempt to access to restricted resources ( like attempt to change reseller info from customer admin resource, change customer info from email_account etc, change other reseller info from other admin account..)

[e-oz]

"login" field for reseller admin and customer admin I can get from getUsername() (if it's not a mistake), but where can I get login for Email Account entity?