UI Integration tests fail on Travis CI

[carltonwhitehead]

TestFX silently fails to click buttons, causing UI integration tests to fail.

[carltonwhitehead]

Noting some observations from first trying to troubleshoot this issue.

• Integration tests pass locally on my laptop, as-is
• Integration tests, if moved into unit test source set and renamed such that Surefire will run them during test instead of Failsafe running them during integrationTest, pass on Travis CI (this is not an acceptable solution because unit tests and integration tests should be separate)
• Integration tests fail on Travis CI whether the TestFX environment is configured for headless or headed