Make N+1 bin optional in histogram

[axelboc]

It's the same issue we had with the heatmap vis: the x axis needs to go up to the right-hand edge of the last bin; otherwise we can't compute the width of the last bar and we get a NaN width warning in the browser console.

This PR makes the extra value in the bins array optional. If it's not present, we assume we want the same step value as between the last and second last bins.

[axelboc]

Perhaps no longer the best name for this hook 😅

[loichuder]

Sorry, I don't get why it should be optional from the description of the issue:

the x axis needs to go up to the right-hand edge of the last bin; otherwise we can't compute the width of the last bar and we get a NaN width warning in the browser console.

Sounds like you do want the last bin, then ? How making it optional helps ?

[axelboc]

Sounds like you do want the last bin, then ? How making it optional helps ?

It depends what you consider to be the "last bin". Basically here, I'm allowing the bins array to have the same size as the values array, which feels more logical (i.e. one bin = one value). The extra item in the bins array (if passed) is purely for plotting purposes, so the idea is for consumers not to have to worry about it.