Use new Calendar API (#249)

Use new Calendar API to add the time separator if two dates are in a different day.

ChattoApp/ChattoApp/Source/ChatItemsDemoDecorator.swift

@@ -54,7 +54,7 @@ final class ChatItemsDemoDecorator: ChatItemsDecoratorProtocol {
                 }
 
                 if let previousMessage = prev as? MessageModelProtocol {
-                    addTimeSeparator = calendar.compare(currentMessage.date, to: previousMessage.date, toGranularity: Calendar.Component.day) != ComparisonResult.orderedSame
+                    addTimeSeparator = !calendar.isDate(currentMessage.date, inSameDayAs: previousMessage.date)
                 } else {
                     addTimeSeparator = true
                 }