Contour plot "undefined" label when z >= 10 million

[ollierob]

When contour z-points are greater than 10 million then the tooltip value is suffixed with "undefined".

The suffix should be B or a multiple of 10M or it should render with an exponent. It should also be implemented for even larger values (1e8+).

var data = [ {
    z: [
        [1e6, 5e6, 1e7, 1.5e7],
        [1.2e6, 5.6e6, 1.1e7, 1.6e7]
    ], type: 'contour'
}];
Plotly.newPlot('myDiv', data);

[alexcjohnson]

Thanks for the report!