Fix flip() example under "Seq is lazy" (immutable-js#1679)

dharkness · leebyron · commit 980f600df815 · 2019-02-13T15:29:44.000-08:00
The Seq example using flip() has an incorrect result (all 1s).
diff --git a/README.md b/README.md
@@ -576,7 +576,7 @@ lazySeq
   .flip()
   .map(key => key.toUpperCase())
   .flip();
-// Seq { A: 1, B: 1, C: 1 }
+// Seq { A: 1, B: 2, C: 3 }
 ```
 
 As well as expressing logic that would otherwise seem memory or time
