Cleanup how koan modules get their intros

test/executor_test.exs

@@ -8,6 +8,10 @@ defmodule ExecuteTest do
   test "stops at the first failing koan" do
     {:failed, %{file: file, line: line}, SampleKoan, _name} = Execute.run_module(SampleKoan)
     assert file == 'test/support/sample_koan.ex'
-    assert line == 4
+    assert line == 8
+  end
+
+  test "can access intro" do
+    assert SampleKoan.intro == "There is something"
   end
 end

test/support/sample_koan.ex

@@ -1,6 +1,10 @@
 defmodule SampleKoan do
   use Koans
 
+  @intro """
+  There is something
+  """
+
   koan "Thinking more than once" do
     assert 3 == ___
     assert 4 == ___