Alternative stream error handling for older Nodes, without stream.pipeline

[tomas]

Fixes #371 (regression introduced in #370)

Handles cleanup of sockets correctly when response stream is piped to a writable one that errors out.

An important note, is that when a writable stream fails, the readable it's reading from isn't aborted but simply unpiped, unless using stream.pipeline. So if you're using resp.pipe(writableStream) in your code, you need to manually abort the request to make sure the socket is properly disposed of, and prevent any possible memleaks because of it. Eg.:

  var resp = needle.get('some.url.com/path')
  var writableStream = fs.createWriteStream('/some/file');
  resp.pipe(writableStream);

  writableStream.on('close', function(e) {
    if (!resp.done) resp.abort();
  })

Or for a shorter version:

  var resp = needle.get('some.url.com/path')
  resp.pipe(fs.createWriteStream('/some/file'))
      .on('close', function(e) { if (!resp.done) resp.abort() })

Remember the Stream#pipe() function returns the destination/writable stream, not the origin/readable one

This PR includes the resp.done boolean that lets you check whether the request completed or not, and the abort() method which is an alias for resp.request.abort().

In short, if you are using a newer version of Node, please use stream.pipeline.