Enhance listStarterkits to return an actual list of starterkit repos

##### Expected Behavior

``` js
pl().liststarterkits(); //=> Promise { <pending> } => [ { name: 'starterkit-mustache-bootstrap', url: 'https://github.com/pattern-lab/starterkit-mustache-bootstrap' }, ...]
```
##### Actual Behavior

``` js
pl().liststarterkits(); //=>  https://github.com/search?utf8=%E2%9C%93&q=starterkit+in%3Aname%2C+user%3Apattern-lab&type=Repositories&ref=searchresults

```
