Remove request path generator

This was useful for a while; however it's no longer needed/is obsolete because:

- the project now uses rspec, whereas the generator still generates test/unit tests
- cucumber specs are no longer desired (and current specs will be ported to rspec features)
- the app will be carved up into several anyway
Delete test_helper because no test/unit tests left
Merge pull request #176 from alphagov/remove-request-path-generator

Remove request path generator