added missing fields of CMakeList.txt

this fixed cmake error for me

example/CMakeLists.txt

 # Copyright (c) 2011 Milo Yip (miloyip@gmail.com)
 # Copyright (c) 2013 Rafal Jeczalik (rjeczalik@gmail.com)
 # Distributed under the MIT License (see license.txt file)
+cmake_minimum_required(VERSION 2.8)
 
 set(EXAMPLES
     capitalize
@@ -13,6 +14,8 @@ set(EXAMPLES
     simplereader
     simplewriter
     tutorial)
+    
+include_directories("../include/")
 
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror -Wall -Wextra -Weffc++ -Wswitch-default")