mcp: [micro-] payment channel client and server in bitcore/JS

[jgarzik]

This is a minimally working prototype of a payment channel client and server, based on the bitcore JS library:

     https://github.com/jgarzik/mcp

It implements the protocol described at https://en.bitcoin.it/wiki/Contracts#Example_7:_Rapidly-adjusted_.28micro.29payments_to_a_pre-determined_party

To review, Mike Hearn did an implementation for bitcoinj a while ago: http://code.google.com/p/bitcoinj/wiki/WorkingWithMicropayments

(though note payments do not necessarily have to be "micro")

[blueadept]

Thank you for this!