Fix gulp & types for gulp to 3 (microsoft#16771)

Author: weswigham

package.json

@@ -34,7 +34,7 @@
         "@types/convert-source-map": "latest",
         "@types/del": "latest",
         "@types/glob": "latest",
-        "@types/gulp": "latest",
+        "@types/gulp": "3.X",
         "@types/gulp-concat": "latest",
         "@types/gulp-help": "latest",
         "@types/gulp-newer": "latest",
@@ -52,7 +52,7 @@
         "chai": "latest",
         "convert-source-map": "latest",
         "del": "latest",
-        "gulp": "latest",
+        "gulp": "3.X",
         "gulp-clone": "latest",
         "gulp-concat": "latest",
         "gulp-help": "latest",