Return numeric values for a range

[Drowze]

I am working on a gem to parse and edit spreadsheets that might contain date and currency cells of any currency (the spreadsheets are from this project: https://aspirebudget.com/). Instead of having to do the hard work of parsing the strings (or calling #numeric_value on each one of them), I want to be able to to have a rows-like method returning only the numeric values (where they apply).

I opened #377 which has a proof of concept of it, adding a couple new the methods to Worksheet: one that should return the rows normally but replacing the numeric_values where they exist (with the notable exception of dirty cells) and one that will return the input_values instead.

Let me know your thoughts :)