Fix incorrect "node-browserify" dev dependency

The module is just called "browserify", not "node-browserify". An `npm install` in this repo fails because of this difference, since a tarball containing a module called "browserify" is downloaded yet `npm` is expecting one containing a "node-browserify" module.

``` bash
$ npm install
npm ERR! Error: Invalid Package: expected node-browserify but found browserify
```

I guess no one has tried running `npm install` here until today: npm/npm#6202