Added pod abstract and some other small changes

Hi,

I added an abstract to the pod for your module. This helps various tools and services process your dist and find an abstract to present for your module (eg MetaCPAN wants it).

I also fixed up module quoting in Makefile.PL so that `perl Makefile.PL` will work, and added the github repo to the metadata (so the repo will appear in the sidebar of MetaCPAN, for example).

Cheers,
Neil