monger.credentials/for => monger.credentials/create

To make sure we don't shadow clojure.core/for when monger.credentials
is required with :refer :all.

src/clojure/monger/credentials.clj

@@ -41,7 +41,7 @@
 ;; API
 ;;
 
-(defn ^MongoCredential for
+(defn ^MongoCredential create
   "Creates a MongoCredential instance with an unspecified mechanism.
    The client will negotiate the best mechanism based on the
    version of the server that the client is authenticating to."

test/monger/test/authentication_test.clj

@@ -37,6 +37,6 @@
 (deftest ^{:authentication true} test-authentication-with-valid-credentials
     ;; see ./bin/ci/before_script.sh. MK.
   (doseq [s ["monger-test" "monger-test2" "monger-test3" "monger-test4"]]
-    (let [creds (mcr/for "clojurewerkz/monger" "monger-test" "monger")
+    (let [creds (mcr/create "clojurewerkz/monger" "monger-test" "monger")
           conn  (mg/connect-with-credentials "127.0.0.1" creds)]
       (mc/remove (mg/get-db conn "monger-test") "documents"))))