Simple applicative lexer based on the article
[Lexical analysis with parser combinators][1]
and the [regex-applicative][2] library.

[1]: https://ro-che.info/articles/2015-01-02-lexical-analysis
[2]: http://hackage.haskell.org/package/regex-applicative-0.3.1/docs/Text-Regex-Applicative.html