separate benchmarks for oscillator vs vibrato test

No worries if you don't want to pull this... it's adding an additional test for 50 audio-rate sine oscillators. I guess at some point we should figure out an interface for running different tests and keep track of different results.
In reality, it would be highly unusual for a Flocking user to create this many synth instances, each containing only a single unit generator. Synths aren't designed to be used like this. To be more accurate to your goal of testing the performance of multiple oscillators running together, this should be factored as a single synth containing "i" sinOsc unit generators summed together. Here's an example:

    var oscillators = [];
    for( var i = 0; i < numberOfOscillators; i++ ) {
        oscillators.push({
            ugen: "flock.ugen.sinOsc",
            freq: 440 + i * 20,
            mul: 1 / length
        });
    }

    var synth = flock.synth({
        synthDef: {
            ugen: "flock.ugen.sum",
            sources: oscillators
        }
    }).play();