Upgraded to gulp-sass 5.0.0 to use node-sass 6.0.0

https://github.com/dlmanning/gulp-sass/blob/978b8f6b48a3d4da1110076b5a246a5e80f7477e/package.json#L46 uses node-sass 6.0.0 which should support Node 12.

Updated gulpfile.js as recommended in https://github.com/dlmanning/gulp-sass#migrating-to-version-5

Ran npm install sass --save-dev to fix errors in npm install.

Author: prameshj

gulpfile.js

@@ -22,7 +22,7 @@ const fse = require('fs-extra');
 const flip = require('gulp-css-flip');
 const gulp = require('gulp');
 const path = require('path');
-const sass = require('gulp-sass');
+const sass = require('gulp-sass')(require('sass'));
 const streamqueue = require('streamqueue');
 const util = require('gulp-util');
 

package.json

@@ -53,9 +53,10 @@
     "gulp-connect": "^5.5.0",
     "gulp-css-flip": "^0.4.0",
     "gulp-css-inline-images": "^0.1.1",
-    "gulp-sass": "^4.1.0",
+    "gulp-sass": "^5.0.0",
     "gulp-util": "^3.0.7",
     "protractor": "^7.0.0",
+    "sass": "^1.49.7",
     "streamqueue": "^1.1.1",
     "webdriver-manager": "^12.1.8"
   },