Versions missing for dependencies

[angelmeraz]

Is there a particular reason why dependencies async and knox do not have a version explicitly set in package.json?

https://github.com/nitaigao/gulp-s3/blob/master/package.json#L26
https://github.com/nitaigao/gulp-s3/blob/master/package.json#L29

On npm install these are being bypassed and not installed, and thus bringing up errors.
As far as I understand, leaving the version empty is not accounted for in semantic versioning: https://docs.npmjs.com/getting-started/semantic-versioning#semver-for-consumers