Fix for setupRefund bug (Issue #19)

[illuzen]

Hey I fixed the bug was preventing the refund exchange from getting thru, cuz we're using bitcore and need payment channel code to work.

It seems to be something to do with how Transaction.change was being used, so I used Transaction.to in place of it, calculating the fees manually.

I tested it on code communicating with BitcoinJ and it successfully did the refund exchange.

Wasn't able to figure out how to do gulp lint etc. on it, as there was no lint target in the gulp file, but I don't understand gulp very well. If anybody wants to help me out with that, I'll run the unit tests and stuff.

[braydonf]

Can you check the status of this with the latest merge?

[illuzen]

It looks like the latest merge covers the issues I was addressing, but more cleanly. Next time!

[illuzen]

I take that back. There's still the issue that setupRefund expects the commitmentTx to have an output, and it doesn't. I think it should be in processFunding:

Consumer.prototype.processFunding = function(utxo) {
$.checkArgument(_.isObject(utxo), 'Can only process an array of objects or an object');
this.commitmentTx.from(utxo);
this.commitmentTx.to(this.commitmentTx.address, utxo.amount - this.commitmentTx.getFee());
};

commitmentTx.address is a P2SH 2-of-2 address with both provider's and consumer's public keys.

Reopening this to get attention on it. I'll make another pull request if it makes sense.