Live DynamoDB tests

- `node test/index.js`: test against local dynalite
- `node test/live.tests.js`: test locally against live DynamoDB. Your environment must be configured with appropriate credentials that can perform pretty much any dynamo action: `dynamodb:*`
- *push a commit*: Travis will perform dynalite tests
- *push a commit with `[live test]` in the message*: Travis will perform live DynamoDB tests
- Live tests work against databases called `dyno-test-{rand}`

#### Next steps
- get it to pass live tests both locally and on Travis. @mick Throughput differences come up right away, and timeouts are a problem.

#25