also:
* updated rubocop and applied styling
* made small test refactorings (using the expect block notation)
* made a small refactor to remove an unnecessary ``return credentials``
* bumped the version
- ServiceAccountCredentials, ServiceAccountJwtHeaderCredentials
and UserRefreshCredentials initializers now take keyword args
via options hash.
- In `credentials_loader.rb`, refactored env var checking into
private methods
- Updated tests & added new tests.
- Fixed existing test for #from_well_known_path 'fails if
the file is invalid', where `from_env` was called instead of
`from_well_known_path`.
- Fixed rubocop errors I introduced, but two existing ones remain.
- Added entry to changelog.
- Fixed rubocop errors from code containing parallel assignments
- Updated rubocop_todo.yml to ignore parallel assignments and
trailing underscore assignments.
Graham Paye
Daniel Azuma
nicholas shook
Vijay Subramani
Tim Emiola
Todd Derr
Herbert Siojo