Address deprecation warning regarding public_folder for Sinatra 1.3+
Address deprecation warning regarding public_folder for Sinatra 1.3+

ming-relax/rollout_ui,duduribeiro/rollout_ui,GhostGroup/rollout_ui,restorando/rollout_ui,ming-relax/rollout_ui,restorando/rollout_ui,GhostGroup/rollout_ui,articulate/rollout_ui,duduribeiro/rollout_ui,GhostGroup/rollout_ui,IoraHealth/rollout_ui,jrallison/rollout_ui,ming-relax/rollout_ui,articulate/rollout_ui,IoraHealth/rollout_ui,duduribeiro/rollout_ui,jrallison/rollout_ui,restorando/rollout_ui,articulate/rollout_ui