fix(package): update @types/gulp to version 4.0.0

https://greenkeeper.io/

package.json

@@ -36,7 +36,7 @@
     "@types/express": "4.0.35",
     "@types/glob": "5.0.30",
     "@types/gm": "1.17.30",
-    "@types/gulp": "3.8.32",
+    "@types/gulp": "4.0.0",
     "@types/gulp-mocha": "0.0.29",
     "@types/gulp-rename": "0.0.31",
     "@types/gulp-tslint": "3.6.30",