Add uri? predicate
Clojure introduced a `uri?` predicate in 1.9. Clojurescript currently doesn't have one.
@dnolen suggested on Slack that it would "probably need to tie to Closure Uri type".
Just require goog.Uri. You don't need to require goog.Uri in the tests.
I don't see why we need a try/catch there. We should remove that. Also don't we need to require goog.Uri?