use gulp last version

Author: Jordi Aguilar

CHANGELOG.md

@@ -11,6 +11,7 @@
 
 ### Changed
 - Prepublish script to postpublish
+- using gulp@^3.9.1 instead of fixed 3.9.1
 
 ## [1.1.0] - 2017-01-10
 ### Changed

package.json

@@ -33,7 +33,7 @@
     "browserify": "13.1.1",
     "convert-source-map": "1.3.0",
     "copyfiles": "1.0.0",
-    "gulp": "3.9.1",
+    "gulp": "^3.9.1",
     "gulp-rename": "1.2.2",
     "gulp-sourcemaps": "1.9.0",
     "gulp-uglify": "2.0.0",