Add `geo.center` attribute to specify map view without rescaling

When using an autosized plot, focusing on a map area by using ranges on scattergeo lat long causes the plot width and height to change. I don’t think this should happen. The plot should always use all available space.

I created a codepen to demonstrate the issue: http://codepen.io/brian428/pen/EWbKgQ

Just change the setRange flag to true to see the effect it has on the plot size.

[brian428]

Here’s an example that shows both problems. At the top of the JS, turn on the scale/rotate to see the map become skewed (zoom out on the map to see it). Then turn that off and turn on the use of a lat/lon range to see the size of the map shrink instead of just scaling the map to show the relevant ranges.

https://codepen.io/brian428/pen/vJZJaE?editors=0010#0

[brian428]

Well the thing that confuses me is that your commit (https://github.com/plotly/plotly.js/commit/4d9b566dbf266f01286dcfbce1149be4bfb76b10) doesn’t look like it has any Plotly changes, only the addition of the mock file. And the release notes don’t mention anything about this issue. So it’s not clear if this functionality is something that already existed and just needed an example provided, or if it involved changes to Plotly that aren’t released yet.