Fixed links to the Artsy pongbot, which now uses playplay.io. [ci skip]
Fixed links to the Artsy pongbot, which now uses playplay.io. [ci skip]

dblock/slack-gamebot,hjdarnel/slack-gamebot,dblock/slack-gamebot,michael-pratt/slack-gamebot,dblock/slack-gamebot,hjdarnel/slack-gamebot,dblock/slack-gamebot,AlexLaviolette/slack-gamebot,michael-pratt/slack-gamebot,hjdarnel/slack-gamebot,michael-pratt/slack-gamebot,hjdarnel/slack-gamebot,michael-pratt/slack-gamebot,AlexLaviolette/slack-gamebot,AlexLaviolette/slack-gamebot,AlexLaviolette/slack-gamebot