Restrict files included in output

[kerrizor]

I'm using this on a repo with a huge number of targets, and it makes the resulting graphs tough to navigate. I wonder if restricting the number of files included in the output analysis would be useful. I could see restricting to only the worst N offenders, or only the files that are in the "upper right" quadrant, or the "worst 50% of files".. or all three. This would require running a full analysis, then processing the result set before beginning graphing. Would also need to add CLI options supporting this.