Add example of lists not support partial match

lib/koans/07_pattern_matching.ex

@@ -55,6 +55,12 @@ defmodule PatternMatching do
     assert make == ___
   end
 
+  koan "Lists must match exactly" do
+    assert_raise ___, fn ->
+      [a, b] = [1,2,3]
+    end
+  end
+
   koan "The pattern can make assertions about what it expects" do
     assert match?([1, _second, _third], ___)
   end

test/koans/patterns_koans_test.exs

@@ -13,6 +13,7 @@ defmodule PatternsTests do
       3,
       "eggs, milk",
       "Honda",
+      MatchError,
       [1,2,3],
       {:multiple, ["Meow", "Woof", "Eh?"]},
       {:multiple, ["Mickey", "Donald", "I need a name!"]},