Add a basic Gitpan::Release object to represent a release.
Add Gitpan::Role::HasCPANPLUS

The only reason we need this is to get at author information.  Probably
more efficient ways to do it, but it works.
Add getting author info for a release.

CPANPLUS is pretty heavy initially getting the author info, but after that its
just a hash lookup.  It works.

Also add some delegation for release and release file info.
Add Gitpan::Role::HasUA to share one LWP::UserAgent between objects.
Add the ability to get a release from BackPAN.
Add code for extracting a release archive.

Decided not to automatically get the archive, but instead throw
an exception.  It would be convenient, but it might also be
redundant.  I dunno.
Make sure everything in a release is readable.

Some releases have messed up permissions.