close() is broken

[morungos]

The close() method fails:

TypeError: Object [object Object] has no method 'close'
  at WordNet.close (/Users/stuart/git/wordnet/lib/wordnet.js:382:20)

It's almost certainly related to my total lack of understanding of util.inherits in Node.js, which was used here as it was in existing code. This should probably use the CS inheritance system for clarity, anyways.

Related to #12