Add conditional logic
Add conditional logic

- Abstracts the version check functionality from `r_version_less_than` into `version_check_less_than`.
- Verify requested image is less than 1.19.2.2 to trigger the osx shortname otherwise use macOS

craigcitro/travis-build,andyli/travis-build,craigcitro/travis-build,andyli/travis-build