Specify a specific version of pytz

Otherwise if you try and install with pip 1.4 you'll get some ridiculous
error because 2013d is a stupid name for a version.

  No distributions matching the version for pytz
Merge pull request #5 from alphagov/fix-stupid-pytz-thing

Specify a specific version of pytz
Add post_deploy hook
Add execute flag to post deploy hook
Merge pull request #6 from alphagov/add-post-deploy-hook

Add post deploy hook