``Axis.automargin`` not there yet

[schlichtanders]

plotly has implemented a crucial automargin flag
https://plot.ly/javascript/setting-graph-size/#automatically-adjust-margins

which essentially fixed this issue with axislabels overlapping long axisticklabels
plotly/plotly.js#1504

would be great if it could be supported

[sbrunk]

@schlichtanders this as well as #41 should work as soon as @alexarchambault cuts a new release.

See https://nbviewer.jupyter.org/github/sbrunk/almond-examples/blob/plotly-automargin/plotly_automargin.ipynb for an example.