Allow [start, stop) representation of survival times

[jwallib]

Hello, I've just discovered the package and it looks great. However, the data I have at the moment uses time-varying covariates so I require compatibility with the [start, stop) representation of survival times. Would it be possible to implement this? Perhaps similar to how glmnet does (see version update 4.1)?

[pbreheny]

I think this is a very good suggestion for something to add to the package, so I'm definitely going to leave this issue open as a new feature request. However, realistically I don't see this being accomplished any time soon unless I find a student/volunteer interested in working on it.