Respect Ruby's verbosity conventions
Set TCP_NODELAY on socket if configured. Can improve persistent conns.
Document TCP_NODELAY option.
Add explicit tcp_nodelay=>false default.
Extract warning logic to `Excon.display_warning`
Merge pull request #229 from brandur/respect-verbosity

Respect Ruby's verbosity conventions
Merge pull request #232 from mheffner/tcp_nodelay2

Add option to set TCP_NODELAY on underlying socket
opt-in for request/response info in HTTPStatusError message

Allow users to restore old error message behavior by choosing to
display the request and/or the response.