log.ticks and precise floats

[nejc0mins]

Similar to #81, except on a log scale.

const testLog = scaleLog().domain([0.15, 0.68]);
console.log(testLog.ticks());

This will output: [0.2, 0.30000000000000004, 0.4, 0.5, 0.6000000000000001]

I am using the latest version (3.2.3)

[mbostock]

I suspect this is only possible if the base is 10 (not in general), so it’ll probably require some special-case logic. I’m not planning on implementing this, but feel free to take a crack at it.