1.4.0
Added PCL Profile259 library.
Added new class NonExistingFile to better manage, well non existing files.
DefaultFileImplementation.Size won't return -1 now if file does not exist, instead, it should throw an exception, check Exist property first.
Renamed PCLExt.FileStorage.Standard.Abstractions to PCLExt.FileStorage.Abstractions
Removed UWP for further investigation. Will be restored with 1.4.1