Update minimum Clojure version to 1.9

Author: weavejester

project.clj

@@ -3,14 +3,12 @@
   :url "https://github.com/ring-clojure/ring-codec"
   :license {:name "The MIT License"
             :url "http://opensource.org/licenses/MIT"}
-  :dependencies [[org.clojure/clojure "1.7.0"]]
+  :dependencies [[org.clojure/clojure "1.9.0"]]
   :plugins [[lein-codox "0.10.7"]]
   :codox
   {:output-path "codox"
    :source-uri "http://github.com/ring-clojure/ring-codec/blob/{version}/{filepath}#L{line}"}
-  :aliases {"test-all" ["with-profile" "default:+1.8:+1.9:+1.10" "test"]}
+  :aliases {"test-all" ["with-profile" "default:+1.10" "test"]}
   :profiles
   {:dev  {:dependencies [[criterium "0.4.6"]]}
-   :1.8  {:dependencies [[org.clojure/clojure "1.8.0"]]}
-   :1.9  {:dependencies [[org.clojure/clojure "1.9.0"]]}
    :1.10 {:dependencies [[org.clojure/clojure "1.10.3"]]}})