ssltest.py: improving ssl versions used.

    sending clienthello with version 03.03 (== tls v1.2) and then sending the
    heartbeat request packet with the version found in the serverhello.

    This makes sure we can check sites which support only tls v1.2,
    and also sites which support only older versions of ssl ( than tls 1.1 )

Also i removed the s.send(hb) in hit_hb, since the hb was already sent from is_vulnerable
and changed the hb packet back to hex, i find that much more readable than escaped ascii.