doc: add security section to README

Author: rvagg

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 [email protected]. 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