Update dev dependency on node-sass to 4.9.3 to mitigate cryptiles vul…

…nerability

Dev dependencies contain `gulp-sass`
which depends on `node-sass`
`node-sass` [`4.9.3` requires `request` `2.87.0`](sass/node-sass#2435)
[`request` `2.87.0` removes dependency on `hawk`](request/request#2943)
`hawk` depends on `cryptiles`
`cryptiles` has the vulnerability https://nvd.nist.gov/vuln/detail/CVE-2018-1000620

package.json

@@ -19,6 +19,7 @@
     "gulp-minify": "^3.0.2",
     "gulp-mustache": "^3.0.1",
     "gulp-sass": "^3.2.1",
+    "node-sass": "^4.9.3",
     "gulp-sourcemaps": "^2.6.4",
     "gulp-uglify": "^3.0.0",
     "gulplog": "^1.0.0",