Fix visual issues in documentation

docs/__init__.py

docs/_build/doctrees/environment.pickle

docs/_build/doctrees/index.doctree

docs/_build/doctrees/source.doctree

docs/_build/html/.buildinfo

docs/_build/html/_sources/source.txt

docs/_build/html/genindex.html

docs/_build/html/index.html

docs/_build/html/objects.inv

docs/_build/html/search.html

docs/_build/html/searchindex.js

docs/_build/html/source.html