Added region option to S3. Fixes #90

Please don't merge this until we sort out the bundler funkiness, as this needs some prerelease testing to make sure this works as expected. According to [this](http://ruby.awsblog.com/post/TxVOTODBPHAEP9/Working-with-Regions) blogpost by amazon `us-east-1` is the default region for the ruby sdk. However, I have been able to push to buckets in different regions before and want to confirm that this doesn't break anything.