Adding x_rate_* properties to all models with X-RateLimit-* header values

There doesn't appear to be any way to avoid hitting a ```429 Too Many Requests``` exception via the Guzzle service. While simply waiting for the exception could work, it doesn't allow you to leave a buffer of remaining calls available for other services and doesn't provide information on when the rate reset will occur.

This pull adds ```x_rate_limit```, ```x_rate_remaining```, and ```x_rate_reset``` properties to all response models, making it simple to throttle from any response.