Update a real channel state on the real blockchain.

[jtremback]

Once https://github.com/jtremback/avocado/issues/2, https://github.com/jtremback/avocado/issues/3 and https://github.com/jtremback/avocado/issues/4 are resolved, we should be able to use the state channels for real.

It would be cool to do this, and also make a video or blog post about it to tell the broader Ethereum community about the good news.