Refactoring noir-auth.core/authenticate

No need to write <del>Java</del> Clojure loops when there are more natural alternatives like HOFs (e.g. [clojure.core/some](http://clojuredocs.org/clojure_core/clojure.core/some)).

(1) is a bit better than (2)

1. `(some #(if (condition) (do-something-and-return-true)) list)`
2. `(loop [lst list item (first list)] (if (nil? item) nil (if (condition) (do-something-and-return-true)))) (recur (next lst) (first lst))`