Update SW help system with the following changes from review:
- Add an "About Sparkling Water" section (and updated the index's "Overview" in the process)
- Add a small overview section about Sparkling and a link to the RSparkling repo
- Change "An Introduction to PySparkling" to just "PySparkling." Added small introductory text with this update.
- Add ellipsis to the "How to" section.