fixed missing include path include

CMakeLists.txt

@@ -34,6 +34,7 @@ include( "src/nett-python/_SourceFiles.cmake" )
 
 include_directories (${ZMQ_INCLUDE_DIR})
 include_directories (${NETT_INCLUDE_DIR})
+include_directories (${NETT_SCHEMA_DIR})
 include_directories (${BOOST_INCLUDE_DIR})
 include_directories (${PYTHON_INCLUDE_DIR})
 include_directories (${PROTOBUF_INCLUDE_DIR})