added --stack option.. refactor

example/stack/cache-control.js

@@ -0,0 +1,23 @@
+'use strict'
+const LocalWebServer = require('../../')
+const cacheControl = require('koa-cache-control')
+const DefaultStack = require('local-web-server-default-stack')
+
+class CacheControl extends DefaultStack {
+  addAll () {
+    this.addLogging('dev')
+      .add({
+        optionDefinitions: {
+          name: 'maxage', type: Number,
+          description: 'The maxage to set on each response.'
+        },
+        middleware: function (options) {
+          return cacheControl({ maxAge: options.maxage })
+        }
+      })
+      .addStatic()
+      .addIndex()
+  }
+}
+
+module.exports = CacheControl