Avoid nil answer, but allow it to fail if it's wrong. Fixes #6.

src/koans/lists.clj

@@ -1,6 +1,6 @@
 (meditations
   "Lists can be expressed by function or a quoted form"
-  (= '(__) (list 1 2 3 4 5))
+  (= '(__ __ __ __ __) (list 1 2 3 4 5))
 
   "They are Clojure seqs (sequences), so they allow access to the first"
   (= __ (first '(1 2 3 4 5)))

src/koans/maps.clj

@@ -24,7 +24,7 @@
   (= __ ({2006 "Torino" 2010 "Vancouver" 2014 "Sochi"} 2010))
 
   "You may not be able to find an entry for a key"
-  (= __ (get {:a 1 :b 2} :c))
+  (= __ (get {:a 1 :b 2} :c :key-not-found))
 
   "You can find out if a key is present"
   (= __ (contains? {:a nil :b nil} :b))