I modified the constantize method to attempt to require the file based on fully qualified name, so if it is available to require you shouldn't have to require it explicitly (although you could - and yes from .metrics would work).

So, ideally I'd think, someone would create custom formatters as their own gem (like [this](https://github.com/fguillen/simplecov-csv)). Throw the gem in the Gemfile, specify the formatter from the command line and you're good to go.