[Image-SIG] Adding Python 3 support

[Brian Crowell]

Hi. I'm interested in helping bring PIL to Python 3.

I contacted Matthias Klose, the package maintainer for PIL, to see
which codebase he thought would be best to do that on, and he pointed
me to Pillow, so I'm here to ask about what's been done so far for
Python 3 support and what I could do.

I noticed there was a patch series porting PIL 1.1.6 to Py3k about
four years ago at https://github.com/sloonz/pil-py3k. Barring anything
else, it seemed like the best plan would be to port that patch series
forward to Pillow, since the hardest thing about the conversion will
be the bytes vs. str division, and that patch series claims to have
worked out a lot of the kinks.

The key question seems to be: What's the earliest version of Python
you would want to support afterwards? Supporting earlier than 2.6
isn't so hard in the C code, but might be difficult in the Python
code.

Let me know your thoughts on this, and if anyone's beaten me to working on this.

--Brian