Strict SSL behavior

[isaacs]

I'd like to add two options:

1. strictSSL flag: Validate the server's certificate, and treat it as an error if there are any problems with it. (This includes self-signed certificates.)
2. ca, key, cert: Just pass-through to the same fields in node's request options.

I'm envisioning something like this:

if (options.strictSSL && !res.connection.pair.cleartext.authorized) {
  var er = new Error(res.connection.pair.cleartext.authorizationError)
  // abort the request, call cb with the error
  // do not upload any bytes.  this is now a security risk.
  // maybe should happen even before headers are sent,
  // since they might include Authorization info?
}

[mikeal]

i would merge this right now but I there's no merge button cause it's not a pull request and I've gotta head up to summer camp :)