Support multiple package names in npm docs | npm home

Currently, you can only get docs for a single package at a time:
```sh
$ npm home express connect # only gets docs for express, ignores second argument
```

This change allows you to specify multiple packages to `npm home`:

```sh
$ npm home express connect # get docs for express & connect
$ npm home express connect mux-demux dnode browserify # get docs for all of these
```