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/readFromStream/readFromStream.cpp

@@ -0,0 +1,30 @@
+#include "json/json.h"
+#include <fstream>
+#include <iostream>
+/** \brief Parse from stream, collect comments and capture error info.
+ * Example Usage:
+ * $g++ readFromStream.cpp -ljsoncpp -std=c++11 -o readFromStream
+ * $./readFromStream
+ * // comment head
+ * {
+ *    // comment before
+ *    "key" : "value"
+ * }
+ * // comment after
+ * // comment tail
+ */
+int main(int argc, char* argv[]) {
+  Json::Value root;
+  std::ifstream ifs;
+  ifs.open(argv[1]);
+
+  Json::CharReaderBuilder builder;
+  builder["collectComments"] = true;
+  JSONCPP_STRING errs;
+  if (!parseFromStream(builder, ifs, &root, &errs)) {
+    std::cout << errs << std::endl;
+    return EXIT_FAILURE;
+  }
+  std::cout << root << std::endl;
+  return EXIT_SUCCESS;
+}