Add a tox.ini
Merge pull request #9 from mgedmin/toxify

Add a tox.ini
Sanitize the Python 2 check.

This broke for me on a project that has a module called 'builtins'.
Let's just do a proper check using the normal `sys.version_info` API.
Merge pull request #20 from nvie/master

Sanitize the Python 2 check
Add failing doctest syntax test
Fix crash when no "offset" in doctest syntax error