[dist] Update dependency concat-stream to v2

Author: renovate-bot

package-lock.json

@@ -18,7 +18,7 @@
   },
   "devDependencies": {
     "async": "^2.0.0",
-    "concat-stream": "^1.6.2",
+    "concat-stream": "^2.0.0",
     "expect.js": "~0.3.1",
     "mocha": "^3.5.3",
     "nyc": "^11.7.1",