Include Q4 2013 data

This includes the latest round of data in the site, in the CSV download
and updates the tests to reflect the new data.

For the record, I did actually go through the tests one-by-one to make
sure they were correct. Pinky promise.
Correct case of 'Total cost'
Remove deprecated flag from pip install
Change which tab is used in Google Spreadsheet

Cliff has started using a different tab in his Google Spreadsheet to
make updates. The ID changed here reflects that change.
Update text on 'About the data'
Merge pull request #145 from alphagov/data-for-q4-2013

Q4 2013 update