Bump to lift-json 2.6-RC1

This bumps things to lift-json 2.6-RC1. Here's the rub: it won't build unless we change `unfiltered-json` to `unfiltered-json4s`. Then if we do that, the main branch of code compiles, but the tests don't.

Wasn't really sure what you wanted to do about this, but this does get lift-json building on 2.11, so I've turned it on for dispatch-all.