Transaction.verifySignature(): no longer require satoshisBuffer param, can call Input method

lib/transaction/transaction.js

@@ -1194,22 +1194,14 @@ Transaction.prototype.isValidSignature = function(signature) {
 /**
  * @returns {bool} whether the signature is valid for this transaction input
  */
-Transaction.prototype.verifySignature = function(sig, pubkey, nin, subscript, sigversion, satoshisBuffer) {
+Transaction.prototype.verifySignature = function(sig, pubkey, nin, subscript, sigversion) {
 
   if (_.isUndefined(sigversion)) {
     sigversion = 0;
   }
 
-  if (_.isUndefined(satoshisBuffer)) {
-    if (sigversion == 1) {
-      throw new errors.Transaction.UnableToVerifySignature(
-          'satoshisBuffer is required when sigversion is 1'
-      );
-    }
-  }
-
   if (sigversion == 1) {
-    return SighashWitness.verify(this, sig, pubkey, nin, subscript, satoshisBuffer);
+    return SighashWitness.verify(this, sig, pubkey, nin, subscript, this.inputs[nin].getSatoshisBuffer());
   }
 
   return Sighash.verify(this, sig, pubkey, nin, subscript);