Registering a key

Hello all. I am still new to node.js and javascript and I am trying to
register a key for
https://hacks.mozilla.org/2013/04/web-payments-with-payswarm-identity-part-1-of-3/
 I get this output when I type "node register-new-key.js" in the terminal
in the payswarm.js/lib directory:
 var nodeContextLoader = jsonld.contextLoaders.node({secure: true});

^
 TypeError: Cannot call method 'node' of undefined
     at Object.<anonymous>
(/home/brent/payswarm.js/lib/payswarm-client.js:1415:47)
     at Module._compile (module.js:456:26)
     at Object.Module._extensions..js (module.js:474:10)
     at Module.load (module.js:356:32)
     at Function.Module._load (module.js:312:12)
     at Module.require (module.js:364:17)
     at require (module.js:380:17)
     at Object.<anonymous>
(/home/brent/payswarm.js/examples/config.js:36:16)
     at Module._compile (module.js:456:26)
     at Object.Module._extensions..js (module.js:474:10)


I believe this is a stack trace. How do I best troubleshoot this?

-Brent