Update README.md

Author: Guillaume Badi

README.md

@@ -43,5 +43,5 @@ result = mailjet.sender.post(data={'email': '[email protected]'})
 ## Combine an resource with an action
 ``` python
 # Get the contact lists of contact #2
-result = mailjet.Contact_getcontactslists(id=2)
+result = mailjet.contact_getcontactslists(id=2)
 ```