updated README.rst for 18b directory

ramalho · ramalho · commit 9b7ee1c0b8c3 · 2015-07-14T00:42:00.000-03:00
diff --git a/18b-async-await/README.rst b/18b-async-await/README.rst
@@ -2,3 +2,10 @@ Sample code for Chapter 18 - "Concurrency with asyncio"
 
 From the book "Fluent Python" by Luciano Ramalho (O'Reilly, 2015)
 http://shop.oreilly.com/product/0636920032519.do
+
+##################################################################
+Note: this "18b" directory contains the examples of chapter 18
+rewritten using the new async/await syntax available in Python 3.5
+only, instead of the "yield-from" syntax which works since Python
+3.3 (and will still work with Python 3.5).
+##################################################################
