GitLab

* python-package: refine plot_tree

This change splits plot_tree to two methods:
1. method of creating digraph of tree
2. method of plotting the digraph with matplotlib

* fix doc

* fix doc

* add plot metrics

* move 'raise Exception' to check_not_tuple_of_2_elements

* rename 'plot_metrics' to 'plot_metric'

* fix misleading message/docs

* change 'Metrics' in title to 'Metric'

* fix misleading comment

* add plot tree

* add docs

* add example

* add test

* fix test

* fix decision type

* add show_info

* use feature name if available

* add plot importance

* add plot example

* format python code with pep8

* **DO NOT MERGE** deliberately break rules to see what will happen during check

* Revert "**DO NOT MERGE** deliberately break rules to see what will happen during check"

This reverts commit 0db93cd7a43c7efa43a2112ada43d46c6f9115d9.

* fix format in test.py

* add docs for pep-8

* add gridsearch example for python sklearn

* reset_learning_rate->reset_parameter

* make callbacks public

Provide a high level Dataset class for easy use.

1. merge python-package
2. add dump model to json
3. fix bugs
4. clean code with pylint
5. update python examples