add note on javac release flag

Signed-off-by: olivier lamy <[email protected]>

Author: olamy

README.md

@@ -1,6 +1,9 @@
 # MojoHaus AnimalSniffer Maven Plugin
 
 This is the [animal-sniffer-maven-plugin](http://www.mojohaus.org/animal-sniffer/animal-sniffer-maven-plugin/).
+
+Please note this plugin is now in maintenance level as the exact same feature can be now easily achieved using the `--release` 
+flag from Javac see (http://openjdk.java.net/jeps/247)
 
 [![Build Status](https://travis-ci.org/mojohaus/animal-sniffer.svg?branch=master)](https://travis-ci.org/mojohaus/animal-sniffer)