doc: add security section to README.md

PR-URL: https://github.com/nodejs/io.js/pull/1948
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

README.md

@@ -280,7 +280,16 @@ Instructions:
   [#io.js on Freenode.net](http://webchat.freenode.net?channels=io.js&uio=d4)
 * [iojs/io.js on Gitter](https://gitter.im/nodejs/io.js)
 
+## Security
 
+All security bugs in io.js are taken seriously and should be reported by
+emailing security@iojs.org. This will be delivered to a subset of the project
+team who handle security issues. Please don't disclose security bugs
+public until they have been handled by the security team.
+
+Your email will be acknowledged within 24 hours, and you’ll receive a more
+detailed response to your email within 48 hours indicating the next steps in
+handling your report.
 
 ## Current Project Team Members