Add option to check host name in amqp ssl transport.

[vickumar1981]

Allows users to create a default ssl context and pass options to that context in the AMQP SSL Transport layer. This allows a user to set custom SSL options for the AMQP connection, such as whether they'd like the certificate's host name to be verified, and whether a certificate is required or not.

-  Allows passing a 'context' attribute to the amqp transport, to override settings for SSL.wrap_socket()
-  If context is not present, falls back to normal functionality of using ssl.wrap_socket()

[ask]

Thanks! Merged into master