Feature/send large message (#14)

* introduce send fragment

* can pass a fin frame

* can send messages which are a perfect multiple of the chunk size

* set fin only for last fragment

* cleanup

* last fragment should be of type CONTINUATION

* Add simple send and receive programs

* speedups receiving + better way to wait for thing

* receive speedup by using linked list of chunks instead of large array

* document bug

* use chunks to receive data

* trailing spaces

ixwebsocket/IXProgressCallback.h

@@ -0,0 +1,14 @@
+/*
+ *  IXProgressCallback.h
+ *  Author: Benjamin Sergeant
+ *  Copyright (c) 2019 Machine Zone, Inc. All rights reserved.
+ */
+
+#pragma once
+
+#include <functional>
+
+namespace ix
+{
+    using OnProgressCallback = std::function<bool(int current, int total)>;
+}