Handle server_hostname and _context in SSLv2 SSLSocket

With the backport of SNI code from Python 3 to Python 2.7.x, Python's
ssl.py is now passing server_hostname and _context into SSLv2's
SSLSocket, rather than just SSLv3's SSLSocket, so we need to handle
those arguments.
Merge pull request #1 from quantopian/ssl2_SSLSocket_arguments

Handle server_hostname and _context in SSLv2 SSLSocket