Account for subprocess cwd bug on Windows.
Internal testing script no longer autoruns tox.
Remove tox from dev requirements.

I consider the dev requirements to be the requirements *within a
virtualenv*. Tox runs by creating these virtualenvs, so there's really
no point in installing tox in virtualenvs that tox creates.
Mention detox in tox.ini.
Add a working template update script.
Remove accidental executable bit.
Drop a version cookie upon project generation.
Remove temp directories upon script completion.
Update PPT version cookie at end of update script.
Give the update script a better name.
Ignore pyenv version files.
Don't append an extra line to the version cookie.
Don't run diff3 on the version cookie.
Only run find_packages on the code package itself.
Do find_packages correctly. Exclude TESTS_DIRECTORY.
Don't require the module's dependencies when importing metadata.
Get rid of the donwload_url keyword.