[WIP] Faraday

@jcwilk Another proof of concept...

I created a Faraday adapter using crystal lake. I'm not sure this is the best strategy for the longterm implementation, but it seems to work.
maybe it'd be worth trying to use faraday+rack in the specs to see what doesn't work. Without experimenting and just by looking through the code it's hard for me to tell how much overlap there is, or to guess about whether it'd be better to wrap crystal_lake around faraday+rack, make it an extension of the faraday rack adapter, replace the rack adapter entirely (as you have here), ditch crystal_lake in lieu of it, etc