[README] explain how to return different values for the same call

README.md

@@ -206,6 +206,17 @@ $user->setName('everzet')->will(function ($args) use ($user) {
 And now it doesn't matter how many times or in which order your methods are called.
 What matters is their behaviors and how well you faked it.
 
+Note: If the method is called several times, you can use the following syntax to return different
+values for each call:
+
+```php
+$prophecy->read('123')->willReturn(1, 2, 3);
+```
+
+This feature is actually not recommended for most cases. Relying on the order of
+calls for the same arguments tends to make test fragile, as adding one more call
+can break everything.
+
 #### Arguments wildcarding
 
 The previous example is awesome (at least I hope it is for you), but that's not