update docs

autoaug/autoaugment_learners/AaLearner.py

autoaug/autoaugment_learners/GruLearner.py

docs/requirements.txt

docs/source/apidoc/autoaug.autoaugment_learners.rst

docs/source/apidoc/autoaug.child_networks.rst

docs/source/apidoc/autoaug.controller_networks.rst

docs/source/apidoc/autoaug.rst

docs/source/apidoc/modules.rst

docs/source/conf.py

docs/source/explanation/learners_theory.rst

docs/source/explanation/problem_setting.rst

docs/source/howto/AaLearner.rst

docs/source/howto/AutoAugment.rst

docs/source/howto/howto_main.rst

docs/source/index.rst

docs/source/installation/installation.rst

...ce/aa_learners/autoaug.autoaugment_learners.AaLearner.rst

...e/aa_learners/autoaug.autoaugment_learners.EvoLearner.rst

...e/aa_learners/autoaug.autoaugment_learners.GruLearner.rst

...ce/aa_learners/autoaug.autoaugment_learners.RsLearner.rst