Extracted StringReader and StringWriter from JsonParser

Split `Internals/` folder into `Data/`, `Deserialization/`, `Serialization/`

include/ArduinoJson/Deserialization/StringWriter.hpp

@@ -0,0 +1,36 @@
+// Copyright Benoit Blanchon 2014-2016
+// MIT License
+//
+// Arduino JSON library
+// https://github.com/bblanchon/ArduinoJson
+// If you like this project, please add a star!
+
+#pragma once
+
+namespace ArduinoJson {
+namespace Internals {
+
+// Parse JSON string to create JsonArrays and JsonObjects
+// This internal class is not indended to be used directly.
+// Instead, use JsonBuffer.parseArray() or .parseObject()
+class StringWriter {
+ public:
+  StringWriter(char *buffer) : _ptr(buffer) {}
+
+  const char *startString() {
+    return _ptr;
+  }
+
+  void stopString() {
+    *_ptr++ = 0;
+  }
+
+  void append(char c) {
+    *_ptr++ = c;
+  }
+
+ private:
+  char *_ptr;
+};
+}
+}