chore(package): update browserify to version 15.1.0

Closes #203

Author: greenkeeper[bot]

package.json

@@ -67,7 +67,7 @@
     "@types/pouchdb-core": "^6.1.9",
     "add-cors-to-couchdb": "0.0.6",
     "brfs": "^1.4.3",
-    "browserify": "^14.5.0",
+    "browserify": "^15.1.0",
     "bundle-collapser": "^1.3.0",
     "chai": "3.5.0",
     "chai-as-promised": "5.3.0",