Heroku has a github integration to handle CI and automatic deploys[1]. This way you can, for example, have your app deployed to heroku automatically when you update master, etc.
Well, he probably means source code management. However...if it's a SaaS you could have the marketing website hosted on github pages for free using Jekyll and that even incorporates a blog into your solution too! Then of course host the app on a subdomain using Heroku. So github can come into it that way if you think about it. Not a bad option at all!
I think the parent meant publish the repo on GitHub as you are unlikely to accidently nuke the code like you would if you were experimenting on Heroku.
