Made Changes file conform to CPAN::Changes::Spec

A lot of changes here, but in summary:

* Added missing dates
* Some 'releases' weren't released. All the ones after Amon2 was released to CPAN I marked as [ ... ] sections in the next release to CPAN.
* All the early pre-CPAN releases marked as 'not released'
* Made formatting more consistent

The online testing service is down at the moment, but I think I've got everything. When the service comes back I'll check, and submit another request if I've missed anything.

Neil