Merge pull request #9 from syohex/correct-rfc-number

Correct RFC number
diff --git a/README.md b/README.md
index d2239a6..21205ea 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 
 # uuid ![build status](https://travis-ci.org/google/uuid.svg?branch=master)
 The uuid package generates and inspects UUIDs based on
-[RFC 412](http://tools.ietf.org/html/rfc4122)
+[RFC 4122](http://tools.ietf.org/html/rfc4122)
 and DCE 1.1: Authentication and Security Services. 
 
 This package is based on the github.com/pborman/uuid package (previously named