fix(package): update browserify to version 15.1.0

Closes #391

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
     "babel-preset-es2015": "6.24.1",
     "babel-preset-react": "6.24.1",
     "babelify": "7.3.0",
-    "browserify": "14.3.0",
+    "browserify": "15.1.0",
     "chai": "4.1.0",
     "chalk": "2.0.0",
     "copyfiles": "1.2.0",