pycares.Channel's default should be None, not -1

[Kentzo]

It's unusual to use -1 as a placeholder for default value. Code that wraps pycares has to either explicitly map None to -1 or expose -1 as a default value. Given that None is widely used, mapping is likely inevitable.

Instead, implementation should be adjusted to allow None as a "use default" placeholder along with -1 for backward compatibility.

[saghul]

Sounds reasonable, I'd take a patch if you're up for it :-)

[saghul]

Fixed in #83