Don't warn if Clojure or ClojureScript are out of date dependencies

[danielcompton]

Clojure and ClojureScript are special dependencies, in that the user is always going to be providing their own version which will override the ones in the project.clj. It is good for projects to maintain backwards compatibility with older versions of Clojure, so they shouldn't be penalised for it, in whatever small way a badge showing outdated dependencies counts as a penalty :)