fix(package): update ws to version 7.1.2

Closes #6

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "noflo-runtime-msgflo": "^0.12.0",
     "noflo-tween": "^0.3.0",
     "noflo-yaml": "^0.4.0",
-    "ws": "^6.1.2"
+    "ws": "^7.1.2"
   },
   "devDependencies": {
     "chai": "^4.2.0",