Y-Axis label padding

Is there a way to adjust the padding between an `outer-middle` y-axis label and the tick labels?

Here's a fiddle: http://jsfiddle.net/jakeorr/fhnqddt6/4/

As you can see, adjusting the font size of the axis label and the tick labels causes an overlap. I'd like to be able to add some padding in there.

Start by reproducing the overlap shown in the linked JSFiddle, focusing on an `outer-middle` y-axis label and its tick labels at different font sizes. Identify how the chart exposes axis-label spacing and make the padding adjustable so the labels no longer overlap; verify the result against the fiddle scenario.

Written by the indexing model from the issue text.