code: function streamToBuffer(stream, cb){ // cb(err, buffer);
      var bufs = [];
      stream.on('data', function(d){
          bufs.push(d);
      })
      .on('end', function(){
          cb(null, Buffer.concat(bufs));
      })
      .on('error', function(err){
          cb(err);
      });
  }
docs: turn stream into buffer
  @param {Object} stream
  @param {Function} cb cb(err, buffer)