This moves churn to use the gem directly opposed to using cmd line interface. This should simplify future changes and updates related to churn.

Added example configuration changes for churn to the .metrics file

Updated the default tmp directory to keep it under the metric_fu structure.

update tests and code.

various improvements and making churn integration a bit simpler

added history update

address some issues

remove unneeded line imporve test
Merge pull request #182 from danmayer/churn_api_interface

Run churn metric as library