The new Sharepoint Online Team Sites with the Office 365 group integration is finally here. As of now you cannot integrate them with an old site collections or sites and they do not show up in the SPO-admin GUI yet. And they still do not have support for third-party apps, but acording to MS it's coming soon.
But it's here for new groups and it looks awesome:
I will definatly play around with these ones and see what I can do with Powershell in the following weeks.