fix: upgrade eslint from 6.5.0 to 6.8.0 (#199)

Snyk has created this PR to upgrade eslint from 6.5.0 to 6.8.0.

See this package in NPM:
https://www.npmjs.com/package/eslint

See this project in Snyk:
https://app.snyk.io/org/nodeshift-agg/project/994c93bd-1c82-4043-8972-3d0873d1a8ec?utm_source=github&utm_medium=upgrade-pr

package.json

@@ -53,7 +53,7 @@
   "devDependencies": {
     "coveralls": "~3.0.9",
     "documentation": "^12.1.4",
-    "eslint": "^6.0.1",
+    "eslint": "^6.8.0",
     "eslint-config-semistandard": "^15.0.0",
     "eslint-config-standard": "^14.1.0",
     "eslint-plugin-import": "~2.20.1",