Added support of String class (issue #55, #56, #70, #77)

include/ArduinoJson/Arduino/String.hpp

@@ -0,0 +1,19 @@
+// Copyright Benoit Blanchon 2014-2015
+// MIT License
+//
+// Arduino JSON library
+// https://github.com/bblanchon/ArduinoJson
+
+#pragma once
+
+#ifndef ARDUINO
+
+#include <string>
+
+typedef std::string String;
+
+#else
+
+#include <WString.h>
+
+#endif