Fixing get flavor details response JSON.

I've added the missing `{` at the very beginning. I've also removed the `limits` property entirely as I don't see [the code](https://github.com/stackforge/poppy/blob/master/poppy/transport/pecan/models/response/flavor.py#L26-L46) generating this property in the JSON. I also verified this by making a live API call and confirming that the `limits` property is absent in the response.

Fixes #13