Histogram reporter

[tsenart]

Viewing latencies distributions in a histogram is useful for certain types of data analysis. This has been originally proposed with #78.

[Mistobaan]

I was working on a PR to enhance the plot reporter, I could look into this with few more specs.
See: https://github.com/Mistobaan/vegeta/compare/feature/add-target-info-to-plot

I think the histogram graph should be contained inside that webpage as well and have some way of selecting what to show. If we could include angularjs embedded it would be a breeze to build a nice UI to switch / toggle different visualizations.

[tsenart]

The histogram reporter I had in mind was a text based one like the text reporter. I like where you're heading with the plot improvements but I don't want to mix that with a histogram.

[tsenart]

https://github.com/tsenart/vegeta/compare/report-hist

[bgentry]

@tsenart the report-hist branch looks great!