Everything has been sort-of hacked together to get something working.  Lots to
do to make it not awful.
o) Make the send and receive processes more asynchronous.  Really want to be
   able to not have to do long, synchronous encryption operations, etc.
o) Make the Crypto* stuff less awful.  It seems like the Method abstraction is
   perhaps not worth it.
o) Do separate algorithm from instance in the SSH code.  It's a mess right now,
   what with the clone() methods.  Yuck.
o) Make sure all those things created by new have appropriate deletes somewhere.
o) Likewise, go over all the RSA, DH, BIGNUM, etc., stuff and add frees.
o) Maybe don't ever generate random padding?
o) Some kind of server public key verification callback.
o) Figure out a naming scheme.  Packet, payload, MACs, etc., all have lots of
   different names.  Hard because we sometimes need to have a Buffer and a
   uint8_t array for the same data.  But the code is hard to read due to all the
   inconsistency and duplication.
o) Figure out a non-OpenSSL BN/mpint representation to use for WANProxy
   generally.
o) Make encode and decode methods have descriptive names rather than having only
   descriptive namespaces.
o) Split up the key exchange input method.  It's harder to check whether its
   variables are used safely since they're in a big, combined lump.