Fixed warning when compiling the example

Using the "quick and dirty configuration" in the example causes a Warning when compiling in recent ClojureScript versions (eg. 0.0-2311) which reads "WARNING: No such namespace: goog.history.EventType at line NN src-cljs/xxx/core.cljs"

In this thread (https://groups.google.com/forum/#!topic/clojurescript/LS9-869QpUU) David Nolen writes that "EventType/NAVIGATE is not supported. There's no truly consistent way to differentiate "static fields" from namespaces. In ClojureScript / always indicates a namespace - nothing else. Use EventType.NAVIGATE instead."