chore(package): update browserify to version 15.2.0

Closes #8

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
   },
   "homepage": "https://github.com/nextorigin/spine-awaitajax#readme",
   "devDependencies": {
-    "browserify": "^14.4.0",
+    "browserify": "^15.2.0",
     "browserify-iced-coffee-coverage": "^1.1.1",
     "coffee-script": "^1.12.7",
     "coveralls": "^2.13.1",