* Changed obfs4proxy to be more like obfsproxy in terms of design,
including being an easy framework for developing new TCP/IP style
pluggable transports.
* Added support for also acting as an obfs2/obfs3 client or bridge
as a transition measure (and because the code itself is trivial).
* Massively cleaned up the obfs4 and related code to be easier to
read, and more idiomatic Go-like in style.
* To ease deployment, obfs4proxy will now autogenerate the node-id,
curve25519 keypair, and drbg seed if none are specified, and save
them to a JSON file in the pt_state directory (Fixes Tor bug #12605).
The same algorithm as ScrambleSuit is used, except:
* SipHash-2-4 in OFB mode is used to create the distribution.
* The system CSPRNG is used when sampling the distribution.
This fixes most of #3, all that remains is generating and sending a
persistent distribution on the server side to the client.
