Follow some conventions

Hi,

These changes get your distribution to follow some of the conventions for modern CPAN/Perl distributions:

 * Added a Changes file, with entries for past releases taken from git log. The contents of this file will be presented by MetaCPAN, and the distribution's home page will show the extract for the most recent release.
 * Explicitly specify 5.8.0 as the minimum version of Perl (due to use of utf8).
 * Added strict and warnings, and made some minor changes so it wouldn't result in errors / warnings.

Neil