Add adapter for HTTP gem

[natematykiewicz]

This PR adds an adapter for the HTTP ruby gem.

I copied a lot from how the Net::HTTP adapter works.

This adapter is a bit difficult, because the HTTP gem has a perform method on its client that takes in a request, builds the connection, and executes it. This means there's not a great way to instantiate a client with a host/port, assert things about its semian_options, and then later actually execute the request.

Typical usage is to call something like HTTP.get(url), which uses this get method, which runs HTTP::Client.new.request(verb, uri).

HTTP::Client.new takes an options argument, but it's just timeout / ssl settings. Nothing regarding the URI.

If anyone has ideas on how to better test that, please let me know. I've run this code in my own project, and it's working well.