removed unused gulp and other build related packages

package.json

@@ -73,19 +73,10 @@
         "eslint-plugin-react": "^7.4.0",
         "eslint-plugin-standard": "^2.0.1",
         "feed": "^4.0.0",
-        "gulp": "^4.0.0",
-        "gulp-concat": "^2.4.1",
-        "gulp-if": "^2.0.0",
-        "gulp-imagemin": "^5.0.3",
-        "gulp-postcss": "^6.0.1",
-        "gulp-rename": "^1.2.2",
-        "gulp-sass": "^4.0.1",
-        "gulp-uglify": "~1.5.0",
         "istanbul": "~0.4.2",
         "mocha": "^6.1.4",
         "node-sass": "^4.12.0",
         "should": "^8.2.2",
-        "vinyl-named": "~1.1.0",
         "webpack": "^4.32.2"
     }
 }