kcar features an HTTP parser that will convert a bytestream into a
3-element array suitable for use as a Rack response. It is IO interface
agnostic, so it may be used with HTTP streams over Unix domain sockets,
regular files, FIFOs, StringIOs as well as traditional TCP sockets.
add Kcar::Parser#body_bytes_left= setter method
This allows us to properly get body_eof? to return true
in Kcar::Response for unchunked responses.