Use instance variables for request/response data.

[frodsan]

I think this would be more friendly for threaded
servers. I think request/response data shouldn't
be shared.

[coveralls]

Coverage increased (+0.6%) to 99.123% when pulling ae90956 on frodsan:fix-server-thread into eb83df7 on hyperoslo:master.

[frodsan]

Here are some examples:

https://github.com/soveran/cuba/blob/master/lib/cuba.rb#L80..L82
https://github.com/sinatra/sinatra/blob/master/lib/sinatra/base.rb#L1488..L1490

[frodsan]

If you want to keep the current version, I think you can use local variables and then pass request and response to receive and verify.

[jgorset]

This is a lot nicer. Thanks @frodsan!