chore(package.json): remove the engineStrict field

The engineStrict field is deprecated in npm 2 and removed in npm 3.

Author: mgol

package.json

@@ -12,7 +12,6 @@
     "node": "<5",
     "npm": "~2.5"
   },
-  "engineStrict": true,
   "scripts": {
     "preinstall": "node scripts/npm/check-node-modules.js --purge",
     "postinstall": "node scripts/npm/copy-npm-shrinkwrap.js",