top level keys in policies are not whitelisted

[rahulreddy]

Policy validator should return false for this policy

{
    "Version": "2012-10-17",
    "Statement": [{
        "Effect": "Allow",
        "Action": ["s3:ListAllMyBuckets", "s3:PutBucket"],
        "Resource": "arn:aws:s3:::*"
    }],
    "Condition": {"DateGreaterThan": { "aws:CurrentTime": "2013-06-30T00:00:00Z"}}
}

In the above policy, Condition is not a valid key.