Add a link to PrePAN from release page

I made some modification according the the discussion below:

* [https://github.com/CPAN-API/metacpan-web/issues/381](https://github.com/CPAN-API/metacpan-web/issues/381)

What I've done are:

* Retrieve module metadata from META.(yml|json)
* Add a link to PrePAN page if available

Please look into the diff and discuss if it should be merged.