Version 1.21
- Added methods firstOrNull(list), firstOrNull(list, pred), lastOrNull(list) and lastOrNull(list, pred) for chain.
- Added methods $.checkNotNull(), Optional.map(function1) and Optional.orThrow(function).
- Changed newHashSet with newLinkedHashSet for uniq/distinct methods.
- Added lastIndex(array), distinct(array) and distinctBy(array, func) methods.
- Added support for the
$.chain(int[]) and $ .map(int[], function) methods.