Allow satoshis to be a string on output creation

lib/transaction/output.js

@@ -43,6 +43,9 @@ Object.defineProperty(Output.prototype, 'satoshis', {
     if (num instanceof BN) {
       this._satoshisBN = num;
       this._satoshis = num.toNumber();
+    } else if (_.isString(num)) {
+      this._satoshis = parseInt(num);
+      this._satoshisBN = BN.fromNumber(this._satoshis);
     } else {
       this._satoshisBN = BN.fromNumber(num);
       this._satoshis = num;

test/transaction/transaction.js

@@ -49,6 +49,11 @@ describe('Transaction', function() {
     object.outputs[0].satoshis.should.equal(testAmount - 10000);
   });
 
+  it('can take a string argument as an amount', function() {
+    var stringTx = new Transaction().to('mrU9pEmAx26HcbKVrABvgL7AwA5fjNFoDc', '10000');
+    (stringTx._outputAmount).should.equal(10000);
+  });
+
   it('returns the fee correctly', function() {
     testTransaction.getFee().should.equal(10000);
   });