Add META_MERGE info to Makefile.PL

* bugtracker:

  This assumes you want to track this project's issues via github.
  If you want to use rt.cpan.org, then don't merge in the `bugtracker'
  part at all. Personally I find Github's issues feature to be easier
  to manage than rt, but your mileage may vary.

* homepage:

  This assumes you haven't created some other homepage for this project.
  If you do create some homepage, using Github pages or just pointing
  to something else, then update the `homepage' entry correctly.

* repository:

  This seems correct for your project. Merging it in will allow sites
  like metacpan.org to offer one-click 'Clone git repository' functionality
  and some basic project stats display; see [here](https://metacpan.org/pod/Test::Resub)
  for an example what that looks like.

Drive-by:
- presumptively updated version to 0.3.1
- updated Changes