Hi there.

I'm quite happy to send these patches in, pplacer has been near the top 
of my most wanted list since I started contributing. There's two parts 
that are a little out of the ordinary:

1) Unfortunately pplacer requires the outdated OCaml 4.01, so I adapted 
the package-with-python2 approach.

2) The pplacer package itself is made up of an OCaml part, plus some 
Python scripts, so I made the scripts a different package and propagated 
that package.

Thanks in advance for any review.

ben.