Return references to resources as URIs in triple export

Schemo:

``` coffee
Foo
  bar:
    refOne myprefix:Quux
```

Instance data

``` coffee
_id: "123"
bar: "http://myprefix/api/quux/321"
```

currently produces

``` turtle
<http://myprefix/api/theClass/123> <http://myprefix/schema/bar> "http://myprefix/api/quux/321"
```

instead of 

``` turtle
<http://myprefix/api/theClass/123> <http://myprefix/schema/bar> <http://myprefix/api/quux/321>
```
