Various updates

Hi Marc,

I've made a number of changes to your dist, mainly to follow various CPAN conventions:

* Added a Changes file, with entries for all previous releases
* Changed dist name to Text-Anagram, following convention of dist name following module name
* Min perl version was set to 5.12, but actually it works fine under 5.6.x
* Updated the pod to follow conventions
* Use the dzil plugin to generate prereqs list, and add github repo to metadata

I'd be happy to do a release if you want to give me co-maint: my PAUSE id is NEILB.

Cheers,
Neil