chore(package): update eslint to version 5.15.2

Closes #20

Author: greenkeeper[bot]

package.json

@@ -23,7 +23,7 @@
     "xml2js": "^0.4.19"
   },
   "devDependencies": {
-    "eslint": "^4.18.0",
+    "eslint": "^5.15.2",
     "eslint-config-prettier": "^2.9.0",
     "eslint-plugin-prettier": "^2.6.0",
     "gulp": "^3.9.1",