Dop

+ Added virtio parameter to create_droplet method
+ Minor fixes in all_ssh_keys method
+ Readme region example now uses to_json() method

+ Added ssh_keys support to Droplet object (thanks to Derek: http://github.com/covertgeek)

+ Added ip_address to Droplet object (thanks to Derek: http://github.com/covertgeek)

+ Added support for requests 1.x (thanks to Luke: http://github.com/clone1018)

+ Initial release