NodeJS import error

I'm trying to use the resemblejs library (http://ift.tt/10MySUZ) to compare two images. However, when I have created a directory and added resemblejs as a dependency, but when I try to run the following: nodejs test.js, I get the following error

var api = resemble(fileData).onComplete(function(data){ ^ ReferenceError: resemble is not defined

I've never used NodeJS before, so it might be something really simple. Any ideas?