Just use autopep8 as part of the build

If a computer is going to moan at me about whitespace, a computer can
fix it.
Merge pull request #365 from alphagov/feature/autopep

Just use autopep8 as part of the build
DRY Request-Id processing
Merge pull request #366 from alphagov/feature/dry-request-id

DRY Request-Id processing
PEP8
Merge pull request #367 from alphagov/flaskutils-pep8

PEP8