[test] Run core tests on npm test

Author: mmalecki

Diff for: package.json

@@ -34,7 +34,7 @@
     "node-http-proxy": "./bin/node-http-proxy"
   },
   "scripts": {
-    "test": "npm run-script test-http && npm run-script test-https",
+    "test": "npm run-script test-http && npm run-script test-https && npm run-script test-core",
     "test-http": "vows --spec && vows --spec --target=https",
     "test-https": "vows --spec --proxy=https && vows --spec --proxy=https --target=https",
     "test-core": "test/core/run"