Update license: Perl 5 -> Artistic 2.0

The original license was the default from Dist::Zilla, which seemed
reasonable at the time: dual-licensed under GPL and Artistic.

However, GitHub doesn't appear to play nice with dual licensing, and
since the Artistic 2.0 license is GPL compatabile, this change appears
to be the right thing to do.
Add README.pod

This is generated via Dist::Zilla::Plugin::ReadmeAnyFromPod, using the
"keep GitHub happy" example from the documentation.
Bump version to v0.003

This is the "make GitHub happy" release.