6.17.7.
Add 6.18.
Check in bootstrap.
Boostrap version of the index page.
Update the index and why pages to use bootstrap.
Boostrap the release page.
Get bootstrap JS working.
Javascript.
Remove a lot of no-longer-used files.
Redirect support.html to /.
Update featured games.
Change button colors.

We use success for positive things (download of stable), and warning
for risky things (prerelease downloads).

This makes important links more obvious, compared to the basic blue
links.