Define channel abstraction, which is hub(signal()).

channel.js

@@ -0,0 +1,17 @@
+/* vim:set ts=2 sw=2 sts=2 expandtab */
+/*jshint asi: true undef: true es5: true node: true browser: true devel: true
+         forin: true latedef: false globalstrict: true */
+
+'use strict';
+
+var hub = require('./hub')
+var signal = require('./signal'),
+    emit = signal.emit, close = signal.close
+
+function channel() {
+  return hub(signal())
+}
+channel.enqueue = emit
+channel.close = close
+
+module.exports = channel