Add Decklin's Command Line slides
Clean up Downloads and Installfest content

This includes:
* Updating Titleizer class to handle hypenated file names and other acronyms
* Rearrange some content for better flow now that we have a sidebar nav to
outline steps
* Modifying link syntax to determine where a page is part of the flow or
extraneous/optional (HTML vs. Markdown) since sidebar is auto-generated