Oh dear. c14n failing in a worrying way.
Add index length to CreateRawUrls migration

This was already in schema.rb, but somehow not the migration. Weird.
Spec correction
Fix Raw::FailedUrl not linking to its Raw::ImportFile. Bump optic14n version to fix path loss.
Be explicit about 0.0.3 of optic14n being broken

https://govuk.campfirenow.com/room/527776/transcript/message/1003563061#message_1003563061
Merge pull request #67 from alphagov/sudden-c14n-wtf

c14n fix/imported raw failed URLs fix
Merge commit '253b20ffc85e7d9171cb127b273392bbf2db9e1e' into HEAD