chore(package): update eslint to version 5.15.2

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "babel-polyfill": "^6.26.0",
     "babel-preset-es2015": "^6.24.1",
     "coveralls": "^3.0.1",
-    "eslint": "^4.19.1",
+    "eslint": "^5.15.2",
     "eslint-config-airbnb-base": "^13.0.0",
     "eslint-plugin-flowtype": "^2.49.3",
     "eslint-plugin-import": "^2.13.0",