Fix pep8 errors
S3Client accepts kwargs and pass them to boto

All options can be inserted in s3 section in config. All values will be
converted to int if possible to allow port etc to be specified.
Fix pep8 errors
Test s3 config from luigi configuration
Merge pull request #500 from campanja/s3client-accept-any-boto-config

S3client accept any boto config
Make S3Target clean up when using format