Add basic file watcher to run koans

lib/meditate.ex

@@ -2,7 +2,10 @@ defmodule Mix.Tasks.Meditate do
   use Mix.Task
 
   def run(_) do
+    Application.ensure_all_started(:elixir_koans)
+    Watcher.start
     Runner.run
+    :timer.sleep(:infinity)
   end
 end
 

lib/runner.ex

@@ -7,10 +7,20 @@ defmodule Runner do
   ]
 
   def run do
+    run(Equalities)
+  end
+
+  def run(start_module) do
     IO.puts("")
-    Enum.take_while(@modules, fn(mod) ->
+    IO.puts("")
+
+    start_idx = Enum.find_index(@modules, &(&1 == start_module))
+    Enum.drop(@modules, start_idx)
+    |> Enum.take_while(fn(mod) ->
       run_module(mod) == :passed
     end)
+
+    IO.puts("")
   end
 
   def run_module(module) do

lib/watcher.ex

@@ -0,0 +1,10 @@
+defmodule Watcher do
+  use ExFSWatch, dirs: ["lib/koans"]
+
+  def callback(file, events)  do
+    if Enum.member?(events, :modified) do
+      [{mod, _}] = Code.load_file(file)
+      Runner.run(mod)
+    end
+  end
+end