Misc distribution udpates

Hi, I've introduced some minor fixes:
* `Changes` file now satisfies [CPAN::Changes::Spec](https://metacpan.org/pod/distribution/CPAN-Changes/lib/CPAN/Changes/Spec.pod). There is a special [online service to check your CPAN uploads](http://changes.cpanhq.org/author/CDYBED) for correctness of the changelog.
* Link to this repository was fixed in `Makefile.PL`.
* `META.yml` file did not show the abstract for the distribution. This has been fixed by adding minimal Pod to the main module.

This PR is part of my [advent quest](https://questhub.io/realm/perl/quest/547b4202070ccf750d00010e).

Cheers,
Sergey.