add menu separator and add -h flag

[bgstack15]

No description provided.

[jonhoo]

Thanks, those seem like good changes overall!
For the separator though, I think with @ckardaris' changes from #8 the idea was to have an empty entry correspond to a separator though. So I think you can just look for an empty menu string and insert a separator for those?

[jonhoo]

I think that if empty string becomes separator, there is no need to also have the ----- variant :)

[bgstack15]

I predict most users will think of "------------" as a separator before they will think of a blank entry. It also provides an easier item to discover when scanning the input string visually. I strongly recommend leaving that option available.

[jonhoo]

I think it's unlikely that a user will know to use exactly as many - as required. They will have to look for "separator" in the help, at which point learning about the empty string is just as easy as learning about the ---- pattern, no?