fix computation of fee without change output

lib/transaction/transaction.js

@@ -845,7 +845,7 @@ Transaction.prototype._clearSignatures = function() {
 };
 
 Transaction._estimateFee = function(size, amountAvailable) {
-  var fee = Math.ceil(size / Transaction.FEE_PER_KB);
+  var fee = Math.ceil(size / 1000) * Transaction.FEE_PER_KB;
   if (amountAvailable > fee) {
     size += Transaction.CHANGE_OUTPUT_MAX_SIZE;
   }