Fix for handling POST data

When executing the code described in the book I get the following output when trying to rename an album:

    {"error":"invalid_json","message":"the provided data is not valid JSON"}

When executing the code hosted on GitHub I get the following output:

    {"error":"invalid_json","message":"the provided data is not valid JSON"}

I can’t say for certain, but I believe the right event is `req.on(‘data’, function(d) {});`.

This pull request contains a version of the code that works with Node v0.5.11-pre on Ubuntu.