Consider creating new Unicode exercise

[soniakeys]

Previous discussion at #195. The Unicode test case was removed from ledger to limit the scope of that exercise. But maybe a new exercise could be created around the idea of that test case. I imagine the original intent of the test case was to show the difference between the bytes of a string and the runes of a string. This is a good start. The Rosetta Code task String length introduces the additional concept of the graphemes of a string. Formatting text in a fixed-pitch font (the subject of ledger) requires yet another width concept ("cell" width, I think) when full-width asian characters are used. And there's more, but that's probably enough for a good exercise.

[petertseng]

Since a new Unicode exercise could be applied to all tracks, I would say this issue should go to x-common. and it's great timing too, since we are talking about that at exercism/problem-specifications#428 ! I'll close this and drop a note in that issue with what I know.