Papermill depends on mime-types >= 1.16

[halostatue]

I'm preparing mime-types 2.0 for release, and it has some breaking API changes (not for most uses, but some esoteric features). The most important API change is that mime-types 2.0 no longer supports Ruby 1.8.

If this matters, the gemspec needs to be changed from >= 1.16 to ~> 1.16.