Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/tzlocal/darwin.py

@@ -1,4 +1,4 @@
-from __future__ import with_statement
+
 import os
 import pytz
 

lib/tzlocal/unix.py

@@ -1,4 +1,4 @@
-from __future__ import with_statement
+
 import os
 import re
 import pytz

lib/tzlocal/win32.py

@@ -1,5 +1,5 @@
 try:
-    import _winreg as winreg
+    import winreg as winreg
 except ImportError:
     import winreg