Geojson zoom on click fixes

[Conengmo]

Close #1345 and close #1162

Apply two changes to the GeoJson class:

Don't zoom on click if the geometry type doesn't support it. This is the case for point geometries.

Add a parameter to control the zoom on click functionality. Disable it by default. I thought about this and I think it's best not to hijack the zoom by default. Users who do want that behavior can enable it as follows:

GeoJson(zoom_on_click=True)

or

choropleth = Choropleth()
choropleth.geojson.zoom_on_click = True

[jtbaker]

This looks great to me @Conengmo. I agree on the default non-zoom-on-click behavior, (although it did feel pretty cool to get that kind of interaction out of the box when first getting started with the library). As a part of this PR, maybe a good thing would be to add the parameter usage to some of the notebook examples so that it's obvious to people when getting started with the library. I'm adding a few ideas as tweaks inline.

[Conengmo]

Thanks for the review Jason!

maybe a good thing would be to add the parameter usage to some of the notebook examples

you're totally right, I'll add that

[jtbaker]

Here, how about to handle zooming for point geometries as well? I'm not sure about best generalized options for the .fitBounds() method, it supports both padding and maxZoom options.

else {
    const targetLatLng = e.target.getLatLng()
    const bounds = L.latLngBounds([targetLatLng, targetLatLng])
    {{ this.parent_map.get_name() }}.fitBounds(bounds, {padding: [5,5], maxZoom: 8});
}

[Conengmo]

I think your code is fine but I'd rather not introduce more fragility here. This may work for point geometries but I'm unsure what new bugs it might introduce. I'll just merge the PR as is, let's consider any new functionality separately.