potential fix for puppet warning

[Neychok]

Would something like this fix https://github.com/garris/BackstopJS/issues/1485 ?

I've never contributed to BackstopJS before so I am sorry if I missed any steps when creating this PR.

Happy to work on this more, if any other changes are required.

[tkrah]

You would need to pass the string "new" to fix that warning - but I can't recommend using new yet, see the issue comment.

[dgrebb]

Thanks for the work on this @Neychok — I submitted a new PR which will work with backwards compatibility in mind.