Replace deprecated dependency gulp-util

[TheDancingCode]

gulp-util has been deprecated recently.

The README.md lists alternatives for all the components so a simple replacement should be enough.

Your package is popular but still relying on gulp-util, it would be good to publish a fixed version to npm as soon as possible.

See:

• https://medium.com/gulpjs/gulp-util-ca3b1f9f9ac5
• Ecosystem migration gulpjs/gulp-util#143

[stephenlacy]

Currently gulp-util is only used for the replaceExtention function, which should be replaced with replace-ext

I can send a PR for that change

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 30 days if no further activity occurs. Thank you for your contributions.

[stephenlacy]

Not stale. I will assume that you want a PR for the changes? Sending one