updated ruby to 2.3.7 in travis config take two

Pull requests into Health Data Standards require the following. Submitter and reviewer should :white_check_mark: when done. For items that are not-applicable, note it's not-applicable ("N/A") and :white_check_mark:.

Submitter:

[x] This pull request describes why these changes were made.
[x] This PR is into the correct branch.
[x] Internal ticket for this PR: https://jira.mitre.org/browse/BONNIE-1772 https://jira.mitre.org/browse/BONNIE-1780
[x] Internal ticket links back to this PR
[x] Code diff has been done and been reviewed (it does not contain: additional white space, not applicable code changes, debug statements, etc.)
[x] Tests are included and test edge cases
[x] Tests have been run locally and pass

Cypress Reviewer:

Name:

[ ] Code is maintainable and reusable, reuses existing code and infrastructure where appropriate, and accomplishes the task’s purpose
[ ] The tests appropriately test the new code, including edge cases
[ ] You have tried to break the code

Bonnie Reviewer:

Name:

[ ] Code is maintainable and reusable, reuses existing code and infrastructure where appropriate, and accomplishes the task’s purpose
[ ] The tests appropriately test the new code, including edge cases
[ ] You have tried to break the code

MeasureAuthoringTool / health-data-standards

updated ruby to 2.3.7 in travis config take two #618