Add continuous integration

[jhsu802701]

Adding continuous integration (with Travis CI, CircleCI, SemaphoreCI, or something similar) and posting the badge on the README.md page provides assurance that the script works properly. The continuous integration can even be set up to automatically upload the resulting ISO files to the testing directory in SourceForge. A cron job can automatically run this script every day or every week. (Admittedly, the continuous integration would only work for 64-bit builds, as Travis CI and similar services don't support 32-bit setups.)