Support relative pointers?

[mokkabonna]

https://tools.ietf.org/html/draft-handrews-relative-json-pointer-01

I have an implementation here. https://github.com/mokkabonna/json-hyper-schema/blob/master/src/relative-json-pointer.js complete with tests: https://github.com/mokkabonna/json-hyper-schema/blob/master/test/specs/relative-json-pointer.spec.js

Would you be willing to implement that in this library? If so I can make a PR.

If not I will publish my implementation as a separate library. I anyway depend on your implementation.