Making `TabViewer::id` mandatory?

[dolezvo1]

Hi, I've been curious if there is a good reason for not making TabViewer::id mandatory, instead of using the Id of the title by default as it works right now. I mean, yes, I suppose the current default implementation is good enough for very simple apps, but it's likely to be much more expensive than Id::new(tab), as well as being incorrect when two tabs have the same title. That means that you have to be aware of the default implementation being less-than-ideal in two subtle ways to use the library correctly. For this reason, I'm not sure it suffices as a good default implementation, but it's just an opinion, of course.

[anhosh]

i think this does make a lot of sense and i quite like this idea. we can make this change in the next minor release :)