Use npm-registry-client instead of npm

Since you're only using `npm.commands.view` it would be better to just use something like:

``` js
var RegClient = require('npm-registry-client')
var client = new RegClient(config)

client.get("npm", "latest", 1000, function (er, data, raw, res) {
// error is an error if there was a problem.
// data is the parsed data object
// raw is the json string
// res is the response from couch
})
```

[npm-registry-client](https://github.com/isaacs/npm-registry-client) is the library depended on by `npm` to fetch things from the registry. Why is this better?
1. **Reduces dependencies:** As a library about dependencies this should be self-explanatory :-D
2. **More configurable:** If I wanted to use `david` to check against two different registries I am currently limited by what is on disk in `.npmrc` when you call `npm.load`

I would make a PR for this if you're interested.