Fix security issues

[deeuu]

└─┬ gulp-sass@3.1.0
  └─┬ node-sass@4.7.2
    └─┬ request@2.79.0
      └─┬ hawk@3.1.3
        ├─┬ boom@2.10.1
        │ └── hoek@2.16.3  deduped
        ├── hoek@2.16.3 
        └─┬ sntp@1.0.9
          └── hoek@2.16.3 

hoek is the offending package, see:
sass/node-sass#2170