Lastest version of swagger-spec-validator (2.3.1) breaks master build

[dtkav]

Description

The latest version of swagger-spec-validator now validates that defaults are the correct type.
Since the library is not pinned, the release has broken master.

(tests/test_api.py::test_other_errors_stop_application_to_setup) relies on the old behavior (don't exit on default type errors if app(debug=true))
Also, one of the test fixtures has a (type: array) without an items: ... block, which is now invalid.

Additional info:

#611 fixes the build by upgrading to the latest version.
An alternate approach would be to pin to 2.0.2 of swagger-spec-validator
Let me know if that's preferred and I can put up a PR.