support specifying initial data for keywords.

clj/clarity/cljs/clarity.cljs

    om/IRender
    (render [_]
      (dom/input #js {:type text
                      :value (om/read d :data)
                      :placeholder ":my.ns/identifier"
                      :pattern "^:(\\w+|\\w+(\\.\\w+)*\\/\\w+)$"
                      :onChange #(change-data % d valid? read-keyword)}))))