message: fix outputs on BTC tx
  closes
diff: @@ -130,11 +130,14 @@ const send = async (from, to, amount) => {
  const fundValue = new BigNumber(String(amount)).multipliedBy(1e8).integerValue().toNumber()
  const feeValue = 5000
  const totalUnspent = unspents.reduce((summ, { satoshis }) => summ + satoshis, 0)
  - const skipValue = totalUnspent - feeValue - fundValue
  + const skipValue = totalUnspent - (fundValue - feeValue)
  unspents.forEach(({ txid, vout }) => tx.addInput(txid, vout, 0xfffffffe))
  - tx.addOutput(to, fundValue)
  + tx.addOutput(to, fundValue - feeValue)
  +
  + if (skipValue > feeValue) {
  tx.addOutput(from, skipValue)
  + }
  tx.inputs.forEach((input, index) => {
  tx.sign(index, keyPair)
  