Update for v4

Updates for v4 and fixes for test errors.

Changes of note:
- Changed `verifications` to `people`
- Changed `watchlist_candidates` to `candidates`
- Changed `QuestionSet` routes to use `question_sets` rather than `questions` as the endpoint
- Locked `minitest` to `~> 4.0.0` in `Gemfile` to assure compatibility with `Test::Unit`, as version 5 of `minitest` will "never be compatible with Test::Unit`
- Changed indentation to use spaces rather than hard tabs in a few files

*Note: I have NOT bumped the version, so that you may select the version number before publishing*

There are **2** failing tests in the test suite, but we have already discussed both of those.