Use absolute import everywhere
This prevents Python 2.7 from attempting to import system modules
like sys and ctypes from the 'serial' directory.
diff --git a/serial/win32.py b/serial/win32.py
index 905ce0f..08b6e67 100644
--- a/serial/win32.py
+++ b/serial/win32.py
@@ -9,6 +9,8 @@
# pylint: disable=invalid-name,too-few-public-methods,protected-access,too-many-instance-attributes
+from __future__ import absolute_import
+
from ctypes import c_ulong, c_void_p, c_int64, c_char, \
WinDLL, sizeof, Structure, Union, POINTER
from ctypes.wintypes import HANDLE