Remove links to outdated demo instance
Clarify and move instructions for contributors above the fold
Fix broken link and update prereqs in install doc
Move contributors link below technical summary for better top to bottom flow
Cleanup links and formatting for README's "how to" sections
Add acronym for Secure Viewing Station, grammar fixes
Recommend removing unneeded hardware from the SVS, and clarify
Explanation and recommendations for possible choices of transfer device
Better organization of howto sections
Remove "before you begin" from README (should be in install docs)
Try different image link on Github
Merge full_install.md into install.md

Also splits the Google Authenticator instructions into a separate
document.
Add TOC to install document
Correct FPF site URL
Correct FPF domain
Correct FPF domain
Update FPF domain
Change pressfreedomfoundation.org to freedom.press
Minor corrections
Merge pull request #737 from freedomofpress/readme-fixes

Merge install docs and update top-level README