Server and client benchmarks show that this makes very little difference
in performance and using dynamic dispatch here is significantly more ergonomic.
This also bounds NetworkStream with Send to prevent incorrect implementations.
Allows the implementation of mock streams for testing and flexibility.
Fixes#5
This introduces a new Trait, NetworkStream, which abstracts over
the functionality provided by TcpStream so that it can be easily
mocked and extended in testing and hyper can be used for
other connection sources.
Introduces two Phantom Types, Fresh and Streaming, which indicate the status
of a Response.
Response::start translates an Response<Fresh> into a
Response<Streaming> by writing the StatusCode and Headers.
Response<Fresh> allows modification of Headers and StatusCode, but does
not allow writing to the body. Response<Streaming> has the opposite privileges.
