add Changes file

Hi,

I've added the change log file following `CPAN::Changes::Spec` format.

Following this format means that various tools can more easily process your distribution automatically.

You can find out more about this at [Brian Cassidy's CPAN::Changes Kwalitee Service](http://changes.cpanhq.org/), which is where I saw your module listed :-)

Cheers,
Sergey