Change date.
[readme] Correct apt-get install layout.

Also, other minor corrections related to unix install.
Remove missing directory
Put debian & homebrew instructions later since they won't be ready at release.
Merge branch 'debian-mods-for-release3.5' of https://github.com/simbody/simbody into debian-mods-for-release3.5
Switch to straight double quotes because the fancy ones which look great when formatted don't display properly in plain text (in vim for example).
Merge pull request #300 from simbody/debian-mods-for-release3.5

Debian changes for 3.5.
[ci skip]