Integer bins via rounding

Just a first pass at doing integer binning via rounding the edges and passing those into the histogram function. In a situation like [25, 81], this will result in 10 bins with a per-bin width of either 5 or 6. If people aren't fans of this, that's totally fine.

I assume I'm doing plenty wrong, too. Please tear me apart!
No need to make a change, but filter seems way nicer to me here, even if you don't want to compress it as much as I would—`return _.filter(records, function(record){…})`. 

Granted, this is coming from someone who wants `(records, path) => _.filter(records, r => _.isFinite(utils.getIn(r, path)))`, so do what you will.