build: bump mocha from 3.0.2 to 5.1.1

Bumps [mocha](https://github.com/mochajs/mocha) from 3.0.2 to 5.1.1.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](mochajs/mocha@v3.0.2...v5.1.1)

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

package.json

@@ -97,7 +97,7 @@
     "karma-sourcemap-loader": "0.3.7",
     "karma-webpack": "3.0.0",
     "marked": "0.3.19",
-    "mocha": "3.0.2",
+    "mocha": "5.1.1",
     "node-sass": "4.7.2",
     "npm-run-all": "2.2.0",
     "null-loader": "0.1.1",