cleanup

* `import os.path` is not required. `import os` is enough.
* Use new-style class.
* Use cut-down division. (`3 / 2` is 1.5 in Python 3)
Remove `is_windows` from Python.
s/PY3K/PY3/
py3: Add unicode=str alias.
python 3: replace `ord()` for mmap compatibility.
Merge pull request #8 from methane/master

Py3対応準備