[product: zaphod][project: zaphod-0.2.2]: Revert to using distools.

SYNOPSIS
[modified]setup.py: Use disttools. It is more widely available.

DETAILS
Reverted to disttools as it seems to be more widely available.
This reverses the decision made to use settuptools in the
previous check in. However the improved behavior of setup
due to correct specficiation of files in the manifest and
the function call remain.