Remove lodash dependency

[epiphone]

Replace lodash function calls with native Javascript code.

[mikeguta]

Hi @epiphone
I have a PR for this by way of introduction. Not sure what the contribution guidelines are, I just tried to keep with the existing style.

[epiphone]

Awesome! I'll review it during the weekend.

[epiphone]

Released in https://github.com/epiphone/class-validator-jsonschema/releases/tag/v3.0.1