depend om snapshot that has primitive cursors.

you have to build it yourself, though. simply clone `swannodette/om` and
run `lein install`.

clj/clarity/project.clj

                 [com.datomic/datomic-free "0.9.4331"]
                 [om "0.1.6"]
                 [om "0.1.7-SNAPSHOT"]
                 [ring "1.2.1"]
                 [compojure "1.1.6"]
  :ring {:handler clarity.server/app}
  :cljsbuild {:crossovers [clarity.types]
              :crossover-path "target/crossover"
              :builds [{:source-paths ["om/src" "cljs"]}]})
              :builds [{:source-paths ["cljs"]}]})