v0.6.0

Added

• Calculation of tax-adjusted returns

Fixed

• Bug in data API that would cause dividends or splits to be duplicated on multiple runs
• Bug in application of corporate actions that caused dividends and splits to be applied in an inconsistent order
  this could result in unpredictable outcomes depending on the order that was used if a stock had a split and
  a dividend on the same day.
• Sortino ratio was showing as NA when it should have been computed