Add Slack link to README, announce new version coming soon

README.md

@@ -1,7 +1,11 @@
-## TV Simulator '99
+# TV Simulator '99
+
+[![Join us on Slack!](https://img.shields.io/badge/join_the_community-on_slack-blue)](https://join.slack.com/t/greenhillplaza/shared_invite/zt-2dq8mx6sm-3YnobHETTmxUNE02TOSPRg)
+
+**Completely redesigned and new version coming soon. Watch this space for updates.**
 
 (AKA Program Guide)
 
 Zach Hall, 2017
 
-[Live Site](http://zshall.github.io/program-guide)
+[Live Site](http://zshall.github.io/program-guide)