message: use v1 transactions on bitcoin spend as well
diff: @@ -1009,6 +1009,7 @@ function makeBitcoinSpend(destinationAddress: string,
  paymentAddress => Promise.all([network.getUTXOs(paymentAddress), network.getFeeRate()])
  .then(([utxos, feeRate]) => {
  const txB = new bitcoinjs.TransactionBuilder(network.layer1)
  + txb.setVersion(1)
  const destinationIndex = txB.addOutput(destinationAddress, 0)
  // will add utxos up to _amount_ and return the amount of leftover _change_
  