possibility to provide region from hiera config

 - `location` was a jimdo-specific fact, so make it configurable
Clarify that we configure more than AWS credentials now
More consistent naming of fixture data
Return early to remove one level of nesting
Document new region config value
Simpler way to retrieve region from AWS config

See http://docs.aws.amazon.com/AWSRubySDK/latest/AWS/Core/Configuration.html
Merge pull request #10 from Jimdo/region_from_config

possibility to provide region from hiera config