Add DialTLS for handshaking amqps:// schemes

Reviewing the continuous integration environment offered by Travis-CI,
RabbitMQ does not listen to any SSL ports so testing is limited to local
with AMQP_URL=amqps://localhost/ with a self-signed cert and trusted
private root CA in the system root CA pool.

  * Strict scheme matching for URL parsing.  If the scheme doesn't have
    a port mapping, then the URL will fail to parse.
  * Fill out the URI.Port field with either the default or specified
    numeric port.
  * Add example for client side of SSL/TLS setup documented here:
    http://www.rabbitmq.com/ssl.html

Schemeless or non AMQP URLs were previously passing URL parsing, now
they are not.
Documentation
TLS socket server test

Exercise DialTLS with a shared root CA to exercise client and server
verification.
errors.New since formatting is not required.
ClientCAs pool is needed for client verification

Avoid using the system CAs for client verification.
Merge pull request #34 from streadway/issue34-tls

Implement TLS