Added configuration for waitUntilSpotInstanceRequestFulfilled().

Added the configuration details to create the **waitUntilSpotInstanceRequestFulfilled()** waiter.

I grabbed the failure status code values from http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-spot-instances-bid-status.html

The waiter works in my code, waiting for the "fulfilled" status, and also throwing an exception if I kill the spot request from the AWS Console, which puts the request into one of the failure statuses.

I did not add a spot instance test in **tests/Aws/Tests/Ec2/Integration/BasicOperationsTest.php**, even though that would be a good next step.