distutils' StrictVersion, with the flexibility of LooseVersion.  It also
deals heuristically with common concepts like alpha/beta/candidate/rc
and pre/preview, as well as '-' and 'pl' branching schemes.

--HG--
branch : setuptools
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/trunk/setuptools%4041000