Add stash indication to mepo status

[mathomp4]

A thought I had. It would be nice if mepo status also listed any stashes you might have. I'm thinking something like:

GMI                    | (t) v1.3.0 (DH) [stashes: 1]

or something.

That way if you want to make sure all code is committed, you don't forget a possible stash.

Yes, you can run mepo stash list but this might inform you you should!