:hackney_options config should be renamed to :httpoison_options

[aaronrenner]

Issue

I was looking through the codebase and noticed that we're actually passing :hackney_options to HTTPoison.

https://github.com/elixir-wallaby/wallaby/blob/4e3818ded8001177a313b85cacaac14244a3303a/lib/wallaby/httpclient.ex#L53-L55

HTTPoison takes slightly different options than hackney, so I'm thinking it would be good to update the config and docs accordingly. We'd probably want to keep :hackney_options working as is, but maybe log a deprecation warning.