Remove npm-check-updates (#164)

Author: goto-bus-stop

package.json

@@ -56,7 +56,6 @@
     "domify": "^1.4.0",
     "from2-string": "^1.1.0",
     "jsdom": "^9.4.2",
-    "npm-check-updates": "^2.2.0",
     "nyc": "^11.9.0",
     "rimraf": "^2.5.1",
     "sheetify-cssnext": "^2.0.1",