chainladder 0.2.6

Enhancements

• Added Triangle.valuation accessor to be used similar to origin and development. This allows for slicing valuations (e.g. diagonals).
• Made triangle arithmetic more robust.
• Extended tail patterns from a point estimate to a one year run-off plus a point estimate. This is to facilitate Actual Vs Expected analysis for the year following an analysis.
• Created Triangle.values property to align with pandas-style syntax.
• Backward compatible to python 3.5