chore(package): update eslint to version 6.8.0

Closes #18

Author: greenkeeper[bot]

package.json

@@ -18,7 +18,7 @@
     "babel-core": "^6.26.0",
     "babel-preset-env": "^1.6.1",
     "babel-preset-flow": "^6.23.0",
-    "eslint": "^4.16.0",
+    "eslint": "^6.8.0",
     "express": "^4.16.2",
     "flow-bin": "^0.89.0",
     "flow-copy-source": "^2.0.2",