Adds speed tests for int2bytes and old_int2bytes.

* In the following tests, the first speed test for
  each version of Python checked is the new
  implementation and the second is the old
  implementation.

$ ./speed.sh
int2bytes speed test
python2.5
1000 loops, best of 3: 315 usec per loop
100 loops, best of 3: 4.87 msec per loop
python2.6
10000 loops, best of 3: 170 usec per loop
100 loops, best of 3: 3.34 msec per loop
python2.7
10000 loops, best of 3: 169 usec per loop
100 loops, best of 3: 2.8 msec per loop
python3.2
10000 loops, best of 3: 169 usec per loop
100 loops, best of 3: 3.16 msec per loop
diff --git a/tests/test_transform.py b/tests/test_transform.py
index ecc1a30..9bd3c6d 100644
--- a/tests/test_transform.py
+++ b/tests/test_transform.py
@@ -3,7 +3,7 @@
 
 import unittest2
 from rsa._compat import b
-from rsa.transform import int2bytes
+from rsa.transform import int2bytes, old_int2bytes
 
 
 class Test_integer_to_bytes(unittest2.TestCase):
@@ -12,13 +12,21 @@
                          b('\x00\x00\x07[\xcd\x15'))
         self.assertEqual(int2bytes(123456789, 7),
                          b('\x00\x00\x00\x07[\xcd\x15'))
+        self.assertEqual(old_int2bytes(123456789, 6),
+                         b('\x00\x00\x07[\xcd\x15'))
+        self.assertEqual(old_int2bytes(123456789, 7),
+                         b('\x00\x00\x00\x07[\xcd\x15'))
 
     def test_raises_OverflowError_when_chunk_size_is_insufficient(self):
         self.assertRaises(OverflowError, int2bytes, 123456789, 3)
         self.assertRaises(OverflowError, int2bytes, 299999999999, 4)
+        self.assertRaises(OverflowError, old_int2bytes, 123456789, 3)
+        self.assertRaises(OverflowError, old_int2bytes, 299999999999, 4)
 
     def test_raises_ValueError_when_negative_integer(self):
         self.assertRaises(ValueError, int2bytes, -1)
+        self.assertRaises(ValueError, old_int2bytes, -1)
 
     def test_raises_TypeError_when_not_integer(self):
         self.assertRaises(TypeError, int2bytes, None)
+        self.assertRaises(TypeError, old_int2bytes, None)