Make Leiningen (more) Eastwood-friendly.

Still get a couple warnings... We don't really care about the
unlimited-use warnings from clojure.test, and there are a couple
warnings we get stemming from bugs/limitations in Eastwood.
Lock on *out* when printing during dependency fetches.
Document various ways to register wagon factories [fixes #1483]
Merge pull request #1493 from tobias/wagon-factory-docs

Document various ways to register wagon factories [fixes #1483]
Depend on latest Pomegranate, fixes #1447.