scala-chart-idiomatic ConfidenceIntervals chart factory

- extracts the re-used newest series data into a separate member
- uses more functional / no side-effect dataset creation
- uses scala-chart XYDeviationChart factory to create the DeviationRenderer
Merge pull request #65 from wookietreiber/wip-confidence-interval-chart-factory

scala-chart-idiomatic ConfidenceIntervals chart factory