Create an example directory and add some code examples. (#944)

* update example directory

* modify some compile error.

* update with clang-format

* update

* update

* add_definitions("../include/json")

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date:      Wed Jul 10 21:26:16 2019 +0800
#
# On branch code_example
# Your branch is up-to-date with 'origin/code_example'.
#
# Changes to be committed:
#	modified:   example/CMakeLists.txt
#

* change CMakeLists.txt

* update streamWrite.cpp

* update

* Update readFromStream.cpp

* fix typo

example/streamWrite/streamWrite.cpp

@@ -0,0 +1,22 @@
+#include "json/json.h"
+#include <iostream>
+/** \brief Write the Value object to a stream.
+ * Example Usage:
+ * $g++ streamWrite.cpp -ljsoncpp -std=c++11 -o streamWrite
+ * $./streamWrite
+ * {
+ *     "Age" : 20,
+ *     "Name" : "robin"
+ * }
+ */
+int main() {
+  Json::Value root;
+  Json::StreamWriterBuilder builder;
+  const std::unique_ptr<Json::StreamWriter> writer(builder.newStreamWriter());
+
+  root["Name"] = "robin";
+  root["Age"] = 20;
+  writer->write(root, &std::cout);
+
+  return EXIT_SUCCESS;
+}