Upgrade ClojureScript to 1806

Our versions of ClojureScript are quite old (almost a year). This pull request is to upgrade our ClojureScript dependency to the latest release [r1806](https://github.com/clojure/clojurescript/tree/r1806).

I'd like to have people try out this version and see if any errors pop up. One particular thing we'd like to do is move from `msg/topic`-style keywords to `:msg/topic`-style keywords (if that feature made it into this release of ClojureScript?)