Security improvement

Created by: ralic

Original Pull Request : https://github.com/gulpjs/gulp/pull/2386

Please reconsider this pull request again because :

1 ) All test passed . https://travis-ci.org/SaferNodeJS/gulp https://travis-ci.org/SaferNodeJS/gulp/builds

Security improvement reported as following Before

added 675 packages from 696 contributors and audited 7707 packages in 65.48s
found 47 vulnerabilities (17 low, 7 moderate, 21 high, 2 critical)
  run `npm audit fix` to fix them, or `npm audit` for details

After Fixing

added 635 packages from 822 contributors and audited 7354 packages in 41.695s
found 0 vulnerabilities