Move documentation to Read the Docs

[wigging]

Currently, the Chemics documentation is manually created with Sphinx and the generated HTML is moved to the chemics.github.io repository. This approach makes chemics.github.io the URL for the documentation.

Use Read the Docs instead of manually creating the documentation. This would make a new URL for the documentation. The old chemics.github.io URL can be used as a landing page for the project.

[wigging]

The chemics.github.io URL now points to the landing page for the project. The chemics.readthedocs.io URL points to the documentation.