Added pod abstract and various other changes

Hi,

I added an abstract to the pod for your module. Various tools and services (such as MetaCPAN and search. cpan.org) expect to find it. You already had the # ABSTRACT comment, so you could also choose to use the PodWeaver plugin to add the abstract.

I made various other changes to follow conventions for distributions.

Also, I was getting a warning to switch to Exporter::Declare::Magic, so I did that. I'm not familiar with Exporter::Declare, so you'll probably want to check that :-) The tests still passed for me though!

Cheers,
Neil