Feature request: Measure metrics on a sub-file basis.

[Chris-May]

Thank you so much for this tool! It's a great idea! You had such a great idea accumulating stats over git commits.

I want to open a discussion to have metrics measured on a finer scale.

After working with some team members to refactor code in a file, several of our wily metrics worsened. This surprised us, so I ran the file through Radon with its function-level reporting, and we could see that while some aggregated file-level metrics were worse, the individual functions were a dramatic improvement.

I've debated requesting this, as I'm sure it adds significant complexity, but I thought the increased resolution into our code bases would help us make better decisions.