Added link to the mailing list.

Author: devjgm

README.md

@@ -2,6 +2,9 @@ This is not an official Google product.
 
 # Overview
 
+**NEW!** Mailing list for users and developers to ask questions about, discuss, and stay up-to-date
+with CCTZ. Please join https://groups.google.com/forum/#!forum/cctz
+
 CCTZ (C++ Time Zone) is a library for translating between absolute times and
 civil times (see the [Fundamental Concepts](#fundamental-concepts) section below for an explanation of
 these terms) using the rules defined by a time zone.