GitLab

If scikit-learn isn't installed (and Read the Docs doesn't have it),
LGBMDeprecated aren't created and can't be imported.

* docs: move files into general

* docs: initial commit for Read the Docs

http://docs.readthedocs.io/en/latest/getting_started.html

just running `sphinx-quickstart`

* docs: update conf.py

* docs: add requirements.txt

* docs: add README.md

* fix tests

* docs: put original docs back