better handling for application statistics

in current version, application statistics always returns as zipped CSV file.
so I've make some modification to this library.

- retrieve CSV file, extract it (if need), then returns merged "ApplicationStatistics" model.
- add find / select features for collections of ApplicationStatistics
- write configuration in any context (like [aws/aws-sdk-ruby](https://github.com/aws/aws-sdk-ruby))
- to reliable spec test, use WebMock instead of your custom mock class.

sorry for my poor code and english.