start to split into node commonjs style modules

- no longer is the global Bitcoin used for modules
- cleaner and more maintainable code
- add more tests

test/integer.js

@@ -0,0 +1,24 @@
+var assert = require('assert');
+var BigInteger = require('../').BigInteger;
+var bytesToHex = require('../').convert.bytesToHex;
+
+test('toByteArraySigned', function() {
+    function hex(num) {
+        var bytes = BigInteger.valueOf(num).toByteArraySigned();
+        var hex = bytesToHex(bytes);
+        return '0x' + hex;
+    }
+
+    assert.equal(hex( 0), '0x');
+    assert.equal(hex( 1), '0x01');
+    assert.equal(hex(-1), '0x81');
+    assert.equal(hex( 127), '0x7f');
+    assert.equal(hex(-127), '0xff');
+    assert.equal(hex( 255), '0x00ff');
+    assert.equal(hex(-255), '0x80ff');
+    assert.equal(hex( 16300),  '0x3fac');
+    assert.equal(hex(-16300), '0xbfac');
+    assert.equal(hex( 62300), '0x00f35c');
+    assert.equal(hex(-62300), '0x80f35c');
+});
+