[Feature Request/Bug] show group's content in all windows

[onlycparra]

Adding more context to #23.

I open a window of firefox.
The sidebar loads and I get the groups with their tabs.
I open a second window of firefox.
The sidebar loads in this second window, but the groups are empty.

I don't know if this is intended to work in that way, or it is a bug. However, having the tabs in all windows is very convenient, because you can deploy your work context in any window, and swap whenever you need.

[Rapptz]

This is intended behaviour. I group by the windowId since most API functions work with the windowID.