Hanging on unicode characters

Hello, great plugin! I was hoping to have a user-defined loop with unicode characters in it.  Trying something minimal like the below, 
```lua
require("boole").setup({ additions = { { "▽", "△" }, },... })
```
leads to either a no-op or a hang when attempting to cycle from ▽ to △, say.

Any idea why? Or ideas for a quick fix? I will also try to look into it.
