use cheap-watch instead of chokidar (#364)

package.json

@@ -19,7 +19,6 @@
     "test": "test"
   },
   "dependencies": {
-    "chokidar": "^2.0.4",
     "html-minifier": "^3.5.16",
     "source-map-support": "^0.5.6",
     "tslib": "^1.9.1"
@@ -30,6 +29,7 @@
     "@types/mocha": "^5.2.5",
     "@types/node": "^10.7.1",
     "@types/rimraf": "^2.0.2",
+    "cheap-watch": "^0.3.0",
     "compression": "^1.7.1",
     "cookie": "^0.3.1",
     "devalue": "^1.0.4",