Node.js release: v0.10.21 and v0.8.26

Change effective on 19 October 2013

Node.js versions 0.8.26 and 0.10.21 have been released and are now available on Heroku. They address a denial-of-service vulnerability in Node’s HTTP stack. For upgrade instructions, see https://devcenter.heroku.com/articles/nodejs-support#specifying-a-node-js-version