Fix string/contains

This fixes `string/contains` to be consistent with it's descriptions, as well as it's implementation in Clojush

src/propeller/push/instructions/string.cljc

@@ -38,7 +38,7 @@
   :string_contains
   ^{:stacks #{:boolean :string}}
   (fn [state]
-    (make-instruction state string/includes? [:string :string] :boolean)))
+    (make-instruction state #(string/includes? %2 %1) [:string :string] :boolean)))
 
 ;; Pushes TRUE if the top CHAR is contained in the top STRING, and FALSE
 ;; otherwise