Remove ruby dependencies from build process

[pjanik]

It includes these changes too: https://github.com/concord-consortium/lab-interactives-site/pull/62

• HAML is replaced with handlebars (using custom conversion script). There's a custom compilation script which replaces script/setup.rb too.
• Ruby SASS is replaced with node SASS.
• Markdown compilation is totally removed. Links to readme and license now go to github. I removed this site: http://lab.concord.org/examples.html as it seems to be outdated and not very useful.
• process-interactives.rb is rewritten in Node.js now
• per-branch config is removed (in /config dir), as it doesn't seem to be used by anyone nowadays.
• Also upated: travis.js config, gemfile, http-server (node instead of rackup), readme.

Demo: http://lab.concord.org/branch/no-ruby/

[scytacki]

I forgot about this. Ugh. It would be great to get it merged in, but now it has conflicts.

Has anyone been using it even though it isn't merged in?

[pjanik]

These conflicts might not be too bad. I kept using the old version, as this PR got lost. Actually, I use guard when I work on Lab interactives, but not sure about other authors. If we have time to fix the conflicts, I'd also try to get 2-3h too to look for guard replacement. Build process of the whole lab-interactives-site is long if I remember correctly, so it's nice when interactive can be updated almost immediately.