v4-to-v5.md

Upgrading from the pre-netstandard Comparers package to the new Nito.Comparers package.

• Code formerly using Comparer<T> and CompareSource should now use ComparerBuilder.

• Similarly, EqualityComparer<T> and EqualityCompareSource have been replaced by EqualityComparerBuilder.

• The anonymous comparers have been removed.

• OrderByDescending and ThenByDescending have been removed; instead, use the descending parameter of OrderBy/ThenBy.

• The allowNulls parameter of all methods has been renamed to specialNullHandling.

• All equality comparer types are in the Nito.Comparers namespace instead of Nito.EqualityComparers.