Support zero-indexed steps

[aloukissas]

It would be great if the library (optionally) allowed for zero-indexed steps. For one, it creates confusion when using the optional nav prop that the nav implementation is an array (zero-indexed). Similar issues arise if the steps themselves are an array of components.

[jcmcneal]

I think this could be added. I assume you're probably working with an iterator like i and don't want to do i + 1?

[aloukissas]

Exactly.

[jcmcneal]

Not sure if this is still a pressing matter, but I do plan to implement zero indexed steps as soon as I can. Sorry it's taking so long.

[daviddavid]

I just started using the wizard, but it seems that SW.state.activeStep is zero-indexed, but the currentStep passed down in the props isn't? Is this intended by design or am I missing something?