Remove response info from OrganisationPresenter

It's not used in any controller.
Remove response info from BasicNeedPresenter

It's not used in any controller
Push response info logic into NeedsController

Response info isn't really anything to do with presenting needs,
so moving the logic to the controller simplifies the presenter a bit.
Inline the OrganisationResultSetPresenter

The presenter is so simple, it's clearer to inline it into the controller.
Presenters should consistently respond to #as_json

Before this change, some responded to #present while
others responded to #as_json.
Merge pull request #73 from alphagov/presenter-improvements

Presenter improvements