Fixes GH-194

The output format is similar to `hexdump -C`

Guaranteeing NULL-termination is very useful when name or value are
used with C functions which requires NULL-terminated string.

OpenSSL 1.0.2 is already released. Avoid the confusing wording that
seems to suggest that a development version of OpenSSL 1.0.2 provides
ALPN support.

For "http" or "https" URIs, :path header field must start with "/".
The only exception is OPTIONS method, which can contain "*" to
represent system-wide OPTIONS request.