Make doc generation recursive

Cakefile

@@ -1,12 +1,22 @@
 task 'test', 'Run the test suite', ->
-    require('nodeunit').reporters.default.run ['./test']
+  require('nodeunit').reporters.default.run ['./test']
 
 task 'docs', 'Generate annotated source code with Docco', ->
-    fs            = require 'fs'
-    {print}       = require 'util'
-    {spawn} = require 'child_process'
-    fs.readdir 'lib', (err, contents) ->
-        files = ("lib/#{file}" for file in contents when /\.coffee$/.test file)
-        docco = spawn 'docco', files
-        docco.stdout.on 'data', (data) -> print data.toString()
-        docco.stderr.on 'data', (data) -> print data.toString()
+  async = require 'async'
+  fs = require 'fs'
+  {print} = require 'util'
+  {exec} = require 'child_process'
+  genDocs = (root) ->
+    fs.readdir root, (err, paths) ->
+      async.forEach paths,
+        (path, cb) ->
+          fs.stat "#{root}/#{path}", (err, stat) ->
+            if stat?.isDirectory()
+              genDocs "#{root}/#{path}"
+            else if /\.coffee$/.test path
+              exec "docco #{root}/#{path}"
+              cb()
+        (err) ->
+          console.error err if err?
+
+  genDocs 'lib'