Add same-codebase support for python 2.7.

When I opted for two codebases for python2/python3,
Send2Trash used C modules and it was easier to just have two
packages. With the ctypes version, supporting both python
versions becomes trivial and it's much more convenient to
merge them back into a single codebase.

I've only tested this code on Linux. I've converted plat_osx and
plat_win, but they only work theoretically.

send2trash/plat_win.py

@@ -1,13 +1,17 @@
-# Copyright 2010 Hardcoded Software (http://www.hardcoded.net)
+# Copyright 2013 Hardcoded Software (http://www.hardcoded.net)
 
 # This software is licensed under the "BSD" License as described in the "LICENSE" file, 
 # which should be included with this package. The terms are also available at 
 # http://www.hardcoded.net/licenses/bsd_license
 
+from __future__ import unicode_literals
+
 from ctypes import windll, Structure, byref, c_uint
 from ctypes.wintypes import HWND, UINT, LPCWSTR, BOOL
 import os.path as op
 
+from .compat import text_type
+
 shell32 = windll.shell32
 SHFileOperationW = shell32.SHFileOperationW
 
@@ -35,8 +39,8 @@ FOF_ALLOWUNDO = 64
 FOF_NOERRORUI = 1024
 
 def send2trash(path):
-    if not isinstance(path, str):
-        path = str(path, 'mbcs')
+    if not isinstance(path, text_type):
+        path = text_type(path, 'mbcs')
     if not op.isabs(path):
         path = op.abspath(path)
     fileop = SHFILEOPSTRUCTW()