Pin engine.io subdependency to avoid issues on Node 6.

Author: Robert Jackson

package.json

@@ -74,5 +74,8 @@
     "github": {
       "release": true
     }
+  },
+  "resolutions": {
+    "**/engine.io": "~3.3.0"
   }
 }

yarn.lock

@@ -3878,7 +3878,7 @@ engine.io-parser@~2.1.0, engine.io-parser@~2.1.1:
     blob "0.0.5"
     has-binary2 "~1.0.2"
 
-engine.io@~3.3.1:
+engine.io@~3.3.0, engine.io@~3.3.1:
   version "3.3.2"
   resolved "https://registry.yarnpkg.com/engine.io/-/engine.io-3.3.2.tgz#18cbc8b6f36e9461c5c0f81df2b830de16058a59"
   integrity sha512-AsaA9KG7cWPXWHp5FvHdDWY3AMWeZ8x+2pUVLcn71qE5AtAzgGbxuclOytygskw8XGmiQafTmnI9Bix3uihu2w==