Fixed pod warning

Hi Ito-san,

I noticed on the [CPANTS dashboard](http://cpants.cpanauthors.org/author/TOSHIOITO) that Web::Dash had a pod error. This pull request fixes that error.

I also updated the formatting of the Changes file to follow CPAN::Changes::Spec, and added a link to the github repo in the pod.

Cheers,
Neil