Add some extra_organisation_slugs for BIS

- Now https://github.com/alphagov/transition/pull/245 is merged, give
  people an example of how to add extra organisation slugs. These are
  real BIS organisations - GO Science and British Hallmarking Council.
Merge pull request #606 from alphagov/add_some_extra_organisation_slugs

Add some extra_organisation_slugs for BIS