Template engine

Since Louis factored out all HTML from qanda and added a configuration file to the templates, it's a small task to add a template engine, replace the PHP views with e.g. Twig templates.

Comparison between Twig and Mustache:

Function	Twig	Mustache
Echo variable	{{var}}	{{var}}
Echo field in variable	{{var.field}}	{{#var}} {{field}} {{/var}}
Loop variable	{% for user in users %} ... {% endfor %}	{{#users}} ... {{/users}}