chore(package): update eslint to version 6.2.1

Closes #20

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
   "devDependencies": {
     "ava": "^0.23.0",
     "babel-eslint": "^8.0.0",
-    "eslint": "^3.10.2",
+    "eslint": "^6.2.1",
     "eslint-config-iansinnott": "^1.0.1",
     "eslint-config-zen": "^3.0.0",
     "eslint-plugin-flowtype": "^2.25.0",