When we do a #fetch on Mogli::User, we should get association relations ...

...(i.e., location)

If you do:
```
u1 = Mogli::User.find(fb_uid, mogli_client)
u1.location # Gets filled
-> bla bla
```
But if you do:
```
u2 = Mogli::User.new({id: fb_uid}, mogli_client)
u2.fetch.location
-> nil
```
This patch fixes this behaviour