Rams dino exercise v2

latest revision
Dinos are already an array. This method should probably not exist at all. Still, if it does, it should probably be called `def to_a`.

A better approach is to define a `to_json` (and possibly a `to_hash`) on Dino. Then you can turn this into:
```
def to_json
  @dinos.to_json
end
```

Nice and clean.