Liquid template variables {{ }} conflict with code blocks

[doomspork]

Liquid assumes all uses of {{ }} are for variables, even inside code blocks. This became apparent when the ETS lesson was deployed:

Liquid Exception: Liquid syntax error: Variable '{{:"$1", :"_", :"$3"}' was not properly terminated with regexp: /\}\}/ in lessons/specifics/ets.md

Temporary workaround is to add a space: { {:"$1", :"_", :"$3"}. Gotta find a better solution.

[milmazz]

@doomspork You can use {% raw %} .. {% endraw %} block, which you can temporarily disables tag processing. I'll fix that in a moment.