One request mapping rebased

[Ryman]

Hey :)

This is a rebase of #111 without the stuff related to inner_hits which seemed to be stalling the PR.

I've also taken minor steps to avoid having a breaking change by removing the old mapping method.

Instead I've opted to deprecate that method and just implement it in terms of the new method (mappings) so that people can update at their leisure.

[benashford]

Thanks for this. I'm running out of time to review this today, but I'll come back to it shortly 👍

[Ryman]

@benashford friendly ping :)