tweak png/jpeg stream examples in source

lib/jpegstream.js

@@ -21,13 +21,7 @@ var Stream = require('stream').Stream;
  *     var out = fs.createWriteStream(__dirname + '/my.jpeg')
  *       , stream = canvas.createJPEGStream();
  *
- *     stream.on('data', function(chunk){
- *       out.write(chunk);
- *     });
- *
- *     stream.on('end', function(){
- *       out.end();
- *     });
+ *     stream.pipe(out);
  *
  * @param {Canvas} canvas
  * @param {Boolean} sync

lib/pngstream.js

@@ -21,13 +21,7 @@ var Stream = require('stream').Stream;
  *     var out = fs.createWriteStream(__dirname + '/my.png')
  *       , stream = canvas.createPNGStream();
  *
- *     stream.on('data', function(chunk){
- *       out.write(chunk);
- *     });
- *
- *     stream.on('end', function(){
- *       out.end();
- *     });
+ *     stream.pipe(out);
  *
  * @param {Canvas} canvas
  * @param {Boolean} sync