A number of fix-ups to the distribution

Hi John,

I've made a number of small changes so your dist follows various conventions:

 * Fixed the abstract in the pod (meant that MetaCPAN, search.cpan.org and others weren't finding an abstract)
 * Added the github repo to the metadata. MetaCPAN will then display it in the sidebar, and other tools can find it.
 * Added min perl version to metadata
 * The doc already mentioned the github repo, I just made it a link.

These sorts of things make it a tad easier to write tools that process CPAN dists automatically.

Cheers,
Neil