3.x-compatible (should be 2.6+/3.2+)

- Cleaned up mix of bytes and str.
- Replaced all the comparing hexlified values, etc., with struct.
- Replaced multi-arg print statements with single-arg print w/format.
- Only tested with 2.7, 3.3, and trunk (pre-3.5)
Make check.py 3.x compatible.

- ...although it doesn't seem to work with pep8 1.3 or later anyway...
Make check.py work with pep8 1.3+

- It was setting options the old-style way.
- The only option it was setting is deprecated.
Add Python 3 trove classifier