chore(package): update eslint to version 6.3.0

Closes #15

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "benchmark": "^2.1.4",
     "chai": "^4.1.2",
     "codecov": "^3.0.2",
-    "eslint": "^4.18.0",
+    "eslint": "^6.3.0",
     "fast-memoize": "^2.3.0",
     "lodash.memoize": "^4.1.2",
     "memoize-one": "^5.0.4",