An IsString (NonEmpty Char) instance

[Henning Thielemann]

On Mon, 4 Sep 2017, Ivan Lazar Miljenovic wrote:

> It's backwards-incompatible, but my preference - especially when you 
> consider the libraries that parse the String - is to have fromString 
> return Maybe.

An expression that is undefined because of "" would become an expression 
that is undefined because of Nothing, right? I do not see a benefit.