so I finally worked out after staring at this for a while why "start" is 4 seconds on this line. It's because the previous commands add up to 4, so we assume they executed in order and so the third command started after the second. Which is probably true, I think, but I'm not sure it's a great idea to do that in the javascript rather than having the server record the start times of the experiments.

I think what this method is REALLY doing is converting Commands (which is not really JSON at this point, it's just a hash, but anyway) in to coordinates for a bar graph. In which case let's call it `toBarGraph(commands)` and have it return e.g. '{label: "dummy3", y: 4, height: 2}'. Then we can have the bar chart be nice and generic and reusable and nothing to do with commands, and this function will just be mapping to that format. What do you think?

Apart from that this all looks good now