Use browserified index.js for bower

I might be completely mistaken since I still struggle with definitions and combinations of `npm`, `bower`, `component` and all the other things in frontend JavaScript. However, when using `d3` with `bower`, only an empty object is returned from a `require("d3")` and indeed, there is only a `return d3` in `d3.js` instead of Node-style `module.exports = d3`. The latter is done with `index-browserify.js` and it seems logical to me to use that for `bower`.

(I've just noticed that I also have to update `bin/bower`, will do so immediately and update the pull request)