Biojs snippets

This PR provides support to run examples of pviz on the biojs registry.
Examples in the folder "snippets" will be shown on registry.biojs.net

The PR includes a grunt task `browserify` to build the browserified version locally.

If you want to test this, run

```
npm install
npm run sniper
```

and open http://localhost:9090/snippets

After you publish this to npm, it might take a bit until the registry lists pviz.