chore(package): update eslint to version 5.15.0

Closes #141

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
   "devDependencies": {
     "babel-preset-steal-test": "0.0.1",
     "chai": "*",
-    "eslint": "^4.19.1",
+    "eslint": "^5.15.0",
     "istanbul": "*",
     "mocha": "4.0.0",
     "q": "^1.5.0",