Add meta tags for search engines
Add freeseer demo video
Fix line breaks using dos2unix
Update references to docs site
Update publish script

- Have it work with the new directory layout,
  though this will probably change soon (see freeseer/freeseer#355).

- Remove old docs before building new ones.
  I realized that some old documentation pages were still being
  hosted when they shouldn't have been, because they were never
  removed.