Lazy error messages

[fsoikin]

Description of the change

fixes #128

• Added a new operator <~?>, which is like <?>, but takes a deferred message - i.e. Unit -> String.
• This is handy when the error message is expensive-ish to construct.
• Made use of this in oneOf, noneOf, oneOfCodePoints, and noneOfCodePoints.
• In all other usages of <?> the error message is either a string literal or a very mall expression, like show c (where c :: Char), which means that in all those cases constructing a closure for deferred message would be more expensive. So I left all those usages alone.

---

Checklist:

• Added the change to the changelog's "Unreleased" section with a link to this PR and your username
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation in the README and/or documentation directory
• Added a test for the contribution (if applicable)