chore(package): update browser-sync to version 2.18.9 (#1951)

https://greenkeeper.io/

package.json

@@ -15,7 +15,7 @@
     "babel-preset-es2015": "~6.24.0",
     "babelify": "~7.3.0",
     "bower": "~1.8.0",
-    "browser-sync": "~2.18.2",
+    "browser-sync": "~2.18.9",
     "browser-sync-spa": "~1.0.3",
     "browserify": "~14.3.0",
     "browserify-istanbul": "~2.0.0",