+ppx_deriving.0.3

0.3
---

  * Show, Eq, Ord, Iter, Fold: handle ref.
  * Show: include break hints in format strings.
  * Show: pull fprintf into local environment.
  * Show: add [@polyprinter] and [@opaque].
@dbuenzli This is also the `{test}` thing, which completely breaks my intent of using opam file for CI... see https://github.com/whitequark/ppx_deriving/blob/master/.travis.yml.

I suppose I'll have to maintain two different opam files for now, but I sure don't want to do this forever.