chore(package): update eslint to version 6.6.0

Closes #5

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
   "devDependencies": {
     "chai": "^4.1.2",
     "coveralls": "^3.0.0",
-    "eslint": "^4.18.2",
+    "eslint": "^6.6.0",
     "eslint-config-airbnb-base": "^13.0.0",
     "eslint-plugin-import": "^2.9.0",
     "mocha": "^5.0.1",