Merge branch 'sphinx'

.gitignore

.readthedocs.yml

doc/Makefile

doc/make.bat

doc/requirements.txt

doc/source/algorithms/VLE.ipynb

doc/source/algorithms/critical_curves.ipynb

doc/source/algorithms/index.rst

doc/source/conf.py

doc/source/derivs/derivs.ipynb

doc/source/derivs/index.rst

doc/source/getting_started/index.rst

doc/source/index.rst

doc/source/models/CPA.ipynb

doc/source/models/PCSAFT.ipynb

doc/source/models/cubics.ipynb

doc/source/models/index.rst

doc/source/models/multifluid.ipynb