Fix the gemspec to dynamically list the test_files
Fix the gemspec to dynamically list the test_files

I keep forgetting what's hard-coded here, so better just to build the list so I
don't have to update it when I remove files

saucelabs/sauce_ruby,saucelabs/sauce_ruby,angelabier1/sauce_ruby,DylanLacey/sauce_ruby,bootstraponline/sauce_ruby,angelabier1/sauce_ruby,bootstraponline/sauce_ruby,anthonywoo/sauce_ruby,angelabier1/sauce_ruby,DylanLacey/sauce_ruby,bootstraponline/sauce_ruby,bootstraponline/sauce_ruby,angelabier1/sauce_ruby,anthonywoo/sauce_ruby