De-selecting area or changing area type: Don't zoom citywide

[gregallensworth]

Noted in https://github.com/GreenInfo-Network/nyc-crash-mapper-chart-view/issues/73#issuecomment-359574748 regarding Intersections, but a good usability move.

• Select an area type, then click an area
• You're zoomed in as expected

Say you want to pan to a neighboring area (easily seen by the sudden cutoff of crashes)

• De-select your area
• See that you are pulled back to citywide view, and have now lost your place visually

Such "visually jarring" behavior has tested poorly on other projects in the past. I would recommend disabling this behavior.

[gregallensworth]

This is now in place. DR has a meeting with client in a few days, to determine whether this new behavior is preferred. If they like it, we can go ahead and close this issue. If not, check the commit and see about undoing the change.

[gregallensworth]

Approved by client.