Minor code improvement for the `gets` function

[beoliver]

friend/src/cemerick/friend/util.clj

Line 4 in 12c5b66

(defn gets

not really that important but the implementation of gets could be cleaner.
would make more sense to be implemented as

(defn gets
  "Returns the first value mapped to key found in the provided maps."
  [k & maps]
  (->> (map #(get % k) maps)
       (remove nil?)
       first))

As you are mapping and filtering nil will never be returned meaning that the threading will continue (= (list) (some->> (map identity []))). If get is used then the call to first will either be a value or nil.