upgrade browserify

I tried to use this in one of my projects. It throws TypeError 

```bash
browserify -t ractify pages/*/**.js -t workerify index.js

path.js:313
        throw new TypeError('Arguments to path.resolve must be strings');
        ^
TypeError: Arguments to path.resolve must be strings
    at Object.exports.resolve (path.js:313:15)
    at /path/to/my/project/node_modules/workerify/node_modules/browserify/node_modules/browser-resolve/index.js:87:32
```

So I upgraded browserify which fixed the exception but it doesn't output anything. I use ractify as another transform. (It needs to be applied before workerify, otherwise it throws an error.) Maybe the problem has something to do with ractify not playing well with workerify. I'm not sure, but changing `on('close')` to `on('end')` fixed it for me.