Tidy up locating wheels to report the wheel's specified Python version
Python version fix for wheel locators - convert to metadata format
Merged in pmoore/distlib (pull request #4)

Tidy up locating wheels to report the wheel's specified Python version
Added CSV code for simplification across 2.x/3.x.
Removed unused Distribution.open_distinfo_file method, simplified CSV use in database, wheel modules.