Update aws-sdk, find_all query options, test cleanup

The find_all method does not pass options along to the underlying query, which is a real problem if you want to do consistent_read. These changes should address the problem:

* AWS::DynamoDB::BatchGet does not support consistent_read in the 5 month old version of aws-sdk, so I updated it to the latest version 1.8.0: 1cf6fa0. 

* To be useful, the query options needed to be exposed in batch_get_item 56061b8 read 3db07cd and find_all bd9ded5. 

* I also cleaned up some of the tests, added a few more and everything is passing.