[opam-devel] OS X pull request testing now active

[Anil Madhavapeddy]

I've added support to our Travis scripts for testing on OSX too, so all new packages will go through Ubuntu and OSX from now on.  Since it's experimental, an OSX failure doesn't mark the whole test as failed.

Depexts for OSX are ["osx" "homebrew"] to permit a future MacPorts depext.

Example:
https://github.com/ocaml/opam-repository/pull/2137
https://travis-ci.org/ocaml/opam-repository/builds/25831552

-anil