python: Port some tests from 2 to 3.

python/test3/test_buffer.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+from nose import main
+from nose.tools import *
+from msgpack import packb, unpackb
+
+def test_unpack_buffer():
+    from array import array
+    buf = array('b')
+    buf.fromstring(packb(('foo', 'bar')))
+    obj = unpackb(buf)
+    assert_equal((b'foo', b'bar'), obj)
+
+if __name__ == '__main__':
+    main()