Installing Travis CLI on Mac

I recently had the need to install the Travis CI CLI tool on my Mac and it turned out to be harder then I would have expected.  The issue came from missing headers for libffi which is usually provided with XCode Command Line Tools...  but since I don't have XCode installed, that library was missing for me.  To resolve the issue I executed the following from a terminal window:

xcode-select --install

I was presented with a dialog to confirm that installation.  The install took a few minutes, when it was complete, I tried the Travis CLI installation again using:

gem install travis

which then completed without error.