Minor cleanup

lib/execute.ex

@@ -1,36 +1,32 @@
 defmodule Execute do
   def run_module(module) do
-    run_until_failure(module, &run_koan/2)
-  end
-
-  def run_until_failure(module, callback) do
-    Enum.reduce_while(module.all_koans, :passed, fn(it, _acc) ->
-      result = callback.(module, it)
-      if result == :passed do
-        {:cont, :passed}
-      else
-        {:halt, result}
-      end
+    Enum.reduce_while(module.all_koans, :passed, fn(koan, _) ->
+      module
+      |> run_koan(koan)
+      |> continue?
     end)
   end
 
+  defp continue?(:passed), do: {:cont, :passed}
+  defp continue?(result), do: {:halt, result}
+
   def run_koan(module, name, args \\ []) do
     parent = self()
-    spawn fn -> exec(module, name, args, parent) end
+    spawn(fn -> exec(module, name, args, parent) end)
     receive do
       :ok   -> :passed
       error -> {:failed, error, module, name}
     end
   end
 
-  def exec(module, name, args, parent) do
+  defp exec(module, name, args, parent) do
     result = apply(module, name, args)
     send parent, expand(result)
     Process.exit(self(), :kill)
   end
 
-  def expand(:ok), do: :ok
-  def expand(error) do
+  defp expand(:ok), do: :ok
+  defp expand(error) do
     {file, line} = System.stacktrace
       |> Enum.drop_while(&in_ex_unit?/1)
       |> List.first