chore: bump node dev dependencies

[palmerabollo]

Bump node dev dependencies to fix two security vulnerabilities reported by github. The security issues only affected two dev dependencies (mocha and coveralls), so the alerts are not critical at all.

I've npm run test and npm run coverage and everything worked as expected.

[coveralls]

Coverage remained the same at 95.652% when pulling 05491f0 on bump_versions into 825455a on master.