Add Python 3 compatibility for the C Extension `_speedups`.

The C Extension should now compile under both Python 2 and 3. I have tested this under version 3.3 and 2.7, and I don't see why there would be problems with other versions.

I ran the test suite with the extension module both disabled and enabled. The results were the same, although several tests failed (I believe due to bytes/unicode issues caused by Python 3 in general).

Of course, I can try to fix bugs that show up in any additional testing you might want to do.

Aaron Jacobs
atheriel@gmail.com