Update README.md

tsung-wei-huang · web-flow · commit a7d3795b4aa3 · 2019-05-16T14:43:26.000-05:00
diff --git a/README.md b/README.md
@@ -52,7 +52,7 @@ See a quick [presentation][Presentation] and
 visit the [documentation][wiki] to learn more about Cpp-Taskflow.
 Technical details can be referred to our [IEEE IPDPS19 paper][IPDPS19].
 
-Notice that starting at v2.2.0 (including this master branch) 
+:exclamation: Notice that starting at v2.2.0 (including this master branch) 
 we isolated the executor interface from Taskflow to improve programming model and performance.
 This introduced a few breaks in using Cpp-Taskflow.
 Please refer to [release-notes](https://cpp-taskflow.github.io/cpp-taskflow/release-2-2-0.html)
