Sorry for so many things in one commit ... it was an iterative
process depending as I worked on BIP32 to get the other stuff
working. (And I was too lazy to separate it out after the fact.)
A breaking change by the array newtyping is that Show for Sha256dHash
now outputs the slice Show. You have to use `{:x}` to get the old hex
output.
A pretty serious oversight :) this was not noticed because I was
simultaneously dealing with a serious tcp connection bug in rustc,
and I had thought bitcoind's angry disconnects were a further
symptom of that.
This is a massive simplification, fixes a couple endianness bugs (though
not all of them I don't think), should give a speedup, gets rid of the
`serialize_iter` crap.
Andrew Poelstra