Use the exposed interface to sighash on tests

test/transaction/sighash.js

@@ -4,9 +4,10 @@ var buffer = require('buffer');
 
 var chai = require('chai');
 var should = chai.should();
-var Script = require('../../lib/script');
-var Transaction = require('../../lib/transaction');
-var sighash = require('../../lib/transaction/sighash');
+var bitcore = require('../../');
+var Script = bitcore.Script;
+var Transaction = bitcore.Transaction;
+var sighash = Transaction.sighash;
 
 var vectors_sighash = require('../data/sighash.json');