Problem with Pygments and Python 3

Hi,

i found that pipe.py throws a TypeError when using Python 3. The reason is in line 40:

```
sys.stdout.write(highlight(code, lexer, formatter))
```

*sys.stdout.write* seems to only accept instances of 'str'. Python 3 returns 'bytes' from the highlight call here. My idea was to check the python version and then act accordingly. I've tested this with Python 2.7.6 and Python 3.3.4 and both worked. But i don't really know a lot about Python so there might be a better solution.

Regards,
Peter