This adds preliminary support for SSL connections to a RabbitMQ
server. Instead of providing two clients (QAmqpClient/QAmqpSslClient),
the SSL support was directly rolled into QAmqpClient itself, providing
signals/slots to deal with errors (sslErrors/ignoreSslErrors), and
the ability to assign a QSslConfiguration. Travis testing for ssl
support is currently disabled, pending a solution to a travis
limitation for starting ssl listeners