chore(package): update eslint to version 6.0.0

Closes #56

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "babel-cli": "^6.18.0",
     "babel-preset-es2015": "^6.18.0",
     "chai": "^3.5.0",
-    "eslint": "^3.10.2",
+    "eslint": "^6.0.0",
     "eslint-config-airbnb-base": "^11.1.2",
     "eslint-plugin-import": "^2.2.0",
     "mocha": "^3.2.0"