fixed year to 2019 in conf.py, helpers.h and LICENSE (dmlc#4661)

Author: turk0v

LICENSE

@@ -186,7 +186,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright (c) 2018 by Contributors
+   Copyright (c) 2019 by Contributors
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

doc/conf.py

@@ -58,7 +58,7 @@
 # General information about the project.
 project = u'xgboost'
 author = u'%s developers' % project
-copyright = u'2016, %s' % author
+copyright = u'2019, %s' % author
 github_doc_root = 'https://github.com/dmlc/xgboost/tree/master/doc/'
 
 os.environ['XGBOOST_BUILD_DOC'] = '1'

tests/cpp/helpers.h

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2016-2018 XGBoost contributors
+ * Copyright 2016-2019 XGBoost contributors
  */
 #ifndef XGBOOST_TESTS_CPP_HELPERS_H_
 #define XGBOOST_TESTS_CPP_HELPERS_H_