Add required require to the wiring file

Add to_param method to attachment s.t. the rails helpers can pick up the
ID's correctly.
Merge pull request #179 from alphagov/add-require-to-wiring

Add required require to the wiring file
Reorder requires in wiring for clarity
Require ManualDocumentValidator in wiring
Require CmaCaseValidator in wiring
Merge pull request #180 from alphagov/bug/require-validator-in-wiring

Require MaunualDocumentValidator in wiring