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!
I usually think of `.ticks()` as the way you get "nice", evenly-spaced values: http://stackoverflow.com/a/20369386/388951