A preliminary pass at number_with_delimiter

This is more to start a conversation as well as provide a possible
single concrete implementation for other things that might go into
Lotus::Helpers:

- I18n
- HTML Safe concerns
I like the separation of Converter and Formatter.

I would also assume that the Converter would transform the primitive (Integer) into a more meaningful object (Temperature). A numerical object with a corresponding unit. Analogous to Ruby's `Array()` method.