Deprecation reason

[andrewthad]

This package is marked as deprecated on hackage. I could imagine dozens of reasons why you would choose to do this, and it doesn't bother me that you did. However, knowing why you did would be helpful for me (and I think for others as well) if we're trying to decide to use this package for something. If it was "I don't want to maintain this anymore, and it won't work with newer versions of lens", then I might still try to use it out for a small project. If it was "The implementation is incorrect and it gives bad results on occasion", then I would never use it. Even adding a one-line explanation of the deprecation reason in the readme would but sufficient for this and helpful for me.

[ekmett]

The main issue is that #15 has never been fixed. If that was fixed I'd undeprecate in a heartbeat, but I haven't had any time to go back and revisit it, so I figured it was safer to just mark the package as deprecated for now.