Set PYTHONUNBUFFERED environment variable

https://docs.python.org/2/using/cmdline.html#envvar-PYTHONUNBUFFERED

Like a lot of things (hi Ruby) Python buffers stdout. This is annoying
in development because it means you might not see the output you're
looking for.

In production-like environments, we should not be putting anything on
stdout that would cause this to be an issue.
Move helpers into their own file

Improve the testing of the requires_authentication decorator. There's
no need to test the decorator in every place that it's used if we
can just test once that it's working.
Add an /upload-data endpoint

The upload endpoint should list the data sets that the user has
access to, and provide a form for each one to allow the user to
upload data.
Make flash messages line up

I don't think .container-fluid should be defined in each of the views.
Add flask integration tests for upload

currently I am having a problem extracting stuff from the session during
tests so we are following redirects to test messages. This is not ideal.
Will try and fix
Working code for the tests we have of upload

We should be able to get these test working without the templates which
will come in the next commit
Template changes to render all the messages upload is now sending out
tests for upload when no file
Fix for upload when no file
pop session stuff, don't just read it - prevent multiple display
improve tests - address issue of having to follow redirects

This means the tests are more unit tests - they no longer have
dependencies on the templates or other upload routes
test session is cleared on sign out
Merge pull request #31 from alphagov/spreadsheets

Spreadsheets
Add signed in decorator to simplify mocking

We can now patch methods on the AdminApi directly as we have a real
session for a user
Merge pull request #32 from alphagov/spreadsheets

Add signed in decorator to simplify mocking
Use INFRASTRUCTURE_ENV for real env

GOVUK_ENV only stores development/production in a rails style switch but
we really want whether we are in preview, staging or production. This
can be retrieved through the INFRASTRUCTURE_ENV variable.
Merge pull request #34 from alphagov/use-real-env

Use INFRASTRUCTURE_ENV for real env