Update dependency coveralls to v3.1.0

Dependency update (patch)

Author: renovate-bot

package-lock.json

@@ -42,7 +42,7 @@
   "homepage": "https://github.com/telemark/node-dsf",
   "devDependencies": {
     "ava": "1.4.1",
-    "coveralls": "3.0.3",
+    "coveralls": "3.1.0",
     "nyc": "14.1.1",
     "standard": "12.0.1"
   },