Update README for Captor syntax

Author: ultrasecreth

README.md

@@ -100,7 +100,9 @@ aMock.stringArgument("it worked!")
 
 verify(aMock).stringArgument(captor)
 
-captor <-> "it worked!"
+captor <-> "it worked!" 
+//or 
+captor shouldHave "it worked!"
 ```
 
 As you can see there is no need to call `capture()` nor `getValue` anymore (although they're still there if you need them)