[Distutils] PEP 376 APIs reworked (was: Re: PEP 376 comments)

[Kevin Teague]

The code is much more readable with the Distribution root name in the
classes now I think.

I've made a small tweak the code and changed the _DistributionMetadata
class to a _parse_distribution_metadata function instead. I think the
code is a bit simpler this way, since then the
DistributionDirectory.metadata attribute is just a straight
distutils.dist.DistributionMetadata class.

http://bitbucket.org/wheat/pep376-minor-refactoring/changeset/c71fa8f3bca5/

(and I hope I've got the bit-bucketery going on correctly here ... I'm
a bitbucket noob)

(oh, and that changeset also contains a t