Add keyword arg "ssl_protocol" to HTTPRequest and set a default of ssl.PROTOCOL_SSLv3

To enable Python 2.6 developers to use TLSv1 in their Secure WebSocket connections, I have added ssl_protocol to the HTTPRequest class as a keyword arg. In addition, I have added to _DEFAULTS with an ssl_protocol value of ssl.PROTOCOL_SSLv3 to maintain backwards compatibility.