Merge pull request #107 from shtukas/introducing-nil

First encounter with `nil`

src/koans/01_equalities.clj

@@ -32,5 +32,8 @@
   "Symbolism is all around us"
   (= 'hello (symbol __))
 
+  "What could be equivalent to nothing?"
+  (= __ nil)
+
   "When things cannot be equal, they must be different"
   (not= :fill-in-the-blank __))