npm install fails in Nodejs v4.0.0

[jdan]

This is because of contextify: brianmcd/contextify#180, which is required by jsdom. We might just need to upgrade jsdom and verify that npm test still works.

If all else fails, maybe add an engines field to package.json? http://stackoverflow.com/questions/29349684/how-can-i-specify-the-required-node-js-version-in-packages-json