README.md: Update CommonMark spec reference to 0.31.
diff --git a/README.md b/README.md
index ac13a06..79ced33 100644
--- a/README.md
+++ b/README.md
@@ -23,7 +23,7 @@ MD4C is Markdown parser implementation in C, with the following features:
* **Compliance:** Generally, MD4C aims to be compliant to the latest version of
[CommonMark specification](http://spec.commonmark.org/). Currently, we are
- fully compliant to CommonMark 0.30.
+ fully compliant to CommonMark 0.31.
* **Extensions:** MD4C supports some commonly requested and accepted extensions.
See below.