Fr rewrite

made this thing more modular. As step 1 of making it better. Want this merged on master before making next changes. 
since the only thing that changes is the uri, I'd be tempted to do this as an `async.each` with the array:

```javascript
["last-day", "last-week", "last-month"]
```

and

```javascript
var url = 'https://api.npmjs.org/downloads/point/' + interval + '/' + p.name;
```