chore(package): update eslint to version 6.7.1

Closes #47

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
   "devDependencies": {
     "ava": "^0.20.0",
     "coveralls": "^2.11.9",
-    "eslint": "^3.1.1",
+    "eslint": "^6.7.1",
     "eslint-config-pedant": "^0.9.0",
     "nyc": "^10.0.0"
   },