Minor modifications

[rstatkevych-guardi]

Hi :)

First of all, thanks for your tool! It was the only thing we could quickly compile for Windows.

I'm not a good Go developer (in fact, it is my first code written in Go) but I needed to modify the tool to adjust it to our needs, and I think this changes could be useful for somebody else, so if it is not too ugly, it won't harm to have it.

1. Added --queries-file flag to pass big amounts of queries in file (queries separated by newlines)
2. Added --json-stats flag to give ability to dump metrics to json file (to make it easy parse-able for automated pipelines)