Dropping support for auth.user/pass

Only accept `username` and `password` as arguments

README.md

@@ -218,11 +218,9 @@ These are the available config options for making requests. Only the `url` is re
   // `auth` indicates that HTTP Basic auth should be used, and supplies credentials.
   // This will set an `Authorization` header, overwriting any existing
   // `Authorization` custom headers you have set using `headers`.
-  // The username can be supplied as `user` or `username`
-  // The password can be supplied as `pass` or `password`
   auth: {
-    user: 'janedoe',
-    pass: 's00pers3cret'
+    username: 'janedoe',
+    password: 's00pers3cret'
   }
 
   // `responseType` indicates the type of data that the server will respond with