[Distutils] Setuptools version parsing changed in SVN

[Phillip J. Eby]

FYI, I've changed the setuptools version parsing scheme.  The release of a 
'Subway 0.2-rc1' today made it clear that the existing scheme was 
unintuitive in how it handled '-' characters, because people expect the '-' 
not to override the 'rc'-ness.

In all previous versions of setuptools, a '-' always meant "this is a 
post-release patch of the thing before the dash".  As of 0.6a9-r41630, 
however, the '-' is ignored when it comes before a prerelease tag like 'rc' 
or 'b' or 'dev', so that the intuitively-expected behavior holds.

This should also fix the existing issues with CherryPy 2.1.0-rc2 and 
similar releases out there.

I've also updated the setuptools doc page with a section on specifying your 
project's version number:

http://peak.telecommunity.com/DevCenter/setuptools#specifying%2Dyour%2Dproject%2Ds%2Dversion

(The advice given there will work for all versions of setuptools, as it is 
based on the less-forgiving algorithm that's already out there.)