chore(package): update browserify to version 15.0.0

Author: greenkeeper[bot]

package.json

@@ -53,7 +53,7 @@
     "babel-register": "^6.26.0",
     "babelify": "^8.0.0",
     "browser-sync": "^2.18.13",
-    "browserify": "^14.4.0",
+    "browserify": "^15.0.0",
     "del": "^3.0.0",
     "dox": "^0.9.0",
     "eslint": "^4.8.0",