Update chai requirement from 4.1.2 to 4.2.0

Updates the requirements on [chai](https://github.com/chaijs/chai) to permit the latest version.
- [Release notes](https://github.com/chaijs/chai/releases)
- [Changelog](https://github.com/chaijs/chai/blob/master/History.md)
- [Commits](chaijs/chai@4.1.2...4.2.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

package.json

@@ -20,7 +20,7 @@
     "http-string-parser": "0.0.6"
   },
   "devDependencies": {
-    "chai": "4.1.2",
+    "chai": "4.2.0",
     "eslint": "4.19.0",
     "eslint-config-airbnb-base": "12.1.0",
     "eslint-plugin-import": "2.17.3",