Add CMake support

Clean up file structure.
Update build scripts.

src/rapidjson_extra.h

@@ -0,0 +1,13 @@
+#ifndef RAPIDJSON_EXTRA_H_INCLUDED
+#define RAPIDJSON_EXTRA_H_INCLUDED
+
+#include <rapidjson/document.h>
+#include <string>
+
+void operator >> (const rapidjson::Value& value, std::string& i);
+void operator >> (const rapidjson::Value& value, int& i);
+std::string GetMember(const rapidjson::Value& value, std::string member);
+void GetMember(const rapidjson::Value& value, std::string member, std::string& target);
+std::string SerializeObject(const rapidjson::Value& value);
+
+#endif // RAPIDJSON_EXTRA_H_INCLUDED