[Fix #269] Ensure namespace sorting does all comparisons as strings

shadow-cljs supports string namespaces for requiring NPM dependencies,
eg:

  (:require [reagent.core :as r]
            ["react-virtualized/dist/commonjs/List" :refer [List]])

By comparing all namespaces as strings, we fix a ClassCast crash trying
to compare such a string to a normal symbol.

Author: dhleong

src/refactor_nrepl/ns/libspecs.clj

@@ -16,7 +16,7 @@
 (defn- aliases-by-frequencies [libspecs]
   (->> libspecs
        (mapcat aliases) ; => [[str clojure.string] ...]
-       (sort-by second)
+       (sort-by (comp str second))
        (group-by first) ; => {str [[str clojure.string] [str clojure.string]] ...}
        (map (comp seq frequencies second)) ; => (([[set clojure.set] 4] [set set] 1) ...)
        (map (partial sort-by second >)) ; by decreasing frequency