Jouri, I agree with Procrastinator (although not the way they said it) you shouldn't put someones name on a paper without them agreeing to it. You may have put some new and interesting ideas in the paper that although worthy of publication weren't ideas he agreed with.

Also you said that group leaders get their names on papers without doing anything well often thats not true. Im not sure about your situation, but often they write the grant proposal for funding for the PhD/PostDoc in the first place and often (in labs) provide equiment and/or reagents that you used to get data with.

Confused, Im sorry but I think you were in the wrong. I guess with both yours and Jouri's situations the moral of the story is to talk to your supervisor (or at the very least email them). Im sure that given a few weeks things will calm down and you'll be back on track.

I hope you things work out with your new supervisor too

"Procrastinator I think its a bit tenuous to compare a PhD student adding her supervisor as a co-author with a guy who added his toddler. I doubt the toddler would have given his dad guidance and advice throughout the PhD process like a supervisor does!"

I was using that as an extreme example of why it was a bad thing to do. However, my underlying point still remains that you shouldn't add someone's name to a paper without their say so.