Update package.json

[dantahoua]

Change version of Gulp for install regarding issue #1322

Before opening a pull request, please make sure to do the following:

Open an issue related to the bugfix/feature addressed in the pull request, if one does not already exist.

Make it clear in your commit messages what is being changed, and the reason for the changes.

[olefredrik]

I agree with @derweili 's comment in #1322

I don't think "next" is the right version to reference. "next" does not reference to a unique version but to the latest stable version. This version will change in the future. Using "next" could cause incompatibility problems when gulp has breaking changes in upcoming versions.

It seems to be a better idea to change it to "gulp": "^4.0"

If you agree that this might be a better approach, please update your pull request and I'll merge it into the master branch.

Thanks!

[dantahoua]

No problem! You're right! I'll update it right now. :)