Add smarty & twig to the example composer.json

[metalmatze]

Isn't it that you have to require smarty or twig to use them?
This should be added to the example composer.json in the readme.

[nsierram]

Agree. I just get this working by adding twig (in my case) to the composer.json file.
Otherwise, fatal errors!

[silentworks]

Ah sorry for that, this is an oversight on my behalf, will fix it soon.

[silentworks]

Added these as suggests, I didn't want to include both as Smarty repo requires the use of SVN and not all user would want to have both Smarty and Twig codebase at the same time. So its down to the user to install which they need.