Streaming exporter

Fixes #125
Closes #177

DiscordChatExporter.Core.Models/MessageGroup.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+
+namespace DiscordChatExporter.Core.Models
+{
+    // Used for grouping contiguous messages in HTML export
+
+    public class MessageGroup
+    {
+        public User Author { get; }
+
+        public DateTimeOffset Timestamp { get; }
+
+        public IReadOnlyList<Message> Messages { get; }
+
+        public MessageGroup(User author, DateTimeOffset timestamp, IReadOnlyList<Message> messages)
+        {
+            Author = author;
+            Timestamp = timestamp;
+            Messages = messages;
+        }
+    }
+}