Make setup.py less Linux-specific, more UNIX-compliant.

- #!/usr/bin/python -> #!/usr/bin/env python
  BSD OS use /usr/local/bin/python

- Man pages location is OS specific.
  For example, this is /usr/local/man on FreeBSD
  or /usr/share/man on Debian.

  I checked several Python projects like Nose-devs,
  it seems there is a consensus to use 'man/manN'.

Change-Id: I584c80c23b1fb9cfe77025d8c93ab9494a7b6cf0

setup.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2010-2011 OpenStack, LLC.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -49,6 +49,6 @@ setup(
     author_email='openstack@lists.launchpad.net',
     url='https://launchpad.net/git-review',
     scripts=['git-review'],
-    data_files=[('share/man/man1', ['git-review.1'])],
+    data_files=[('man/man1', ['git-review.1'])],
     install_requires=['argparse'],
 )