Fix payout tests (#74)

* Fix payout tests

* update travis file

* update travis file

* upgrade pip for CI

* travis file add update before install

* Update .travis.yml

Author: AlexandrosMor

Adyen/client.py

@@ -233,7 +233,7 @@ def call_api(self, request_data, service, action, idempotency=False,
             username = self.username
         elif 'username' in kwargs:
             username = kwargs.pop("username")
-        elif service == "Payout":
+        if service == "Payout":
             if any(substring in action for substring in
                    ["store", "submit"]):
                 username = self._store_payout_username(**kwargs)
@@ -254,7 +254,7 @@ def call_api(self, request_data, service, action, idempotency=False,
             password = self.password
         elif 'password' in kwargs:
             password = kwargs.pop("password")
-        elif service == "Payout":
+        if service == "Payout":
             if any(substring in action for substring in
                    ["store", "submit"]):
                 password = self._store_payout_pass(**kwargs)