Fix module/class resolution bugs in SmartdownAdaptor

This was only happening in production mode, not dev, due to different class loading/caching behaviour.

Because the App presenters (for smart_answers) aren't namespaced by a module they will get picked over `SmartdownAdapter` versions, due to ruby scoping/resolution rules (related, http://techblog.thescore.com/how-you-nest-modules-matters-in-ruby/)

This commit makes sure we explicitly use `SmartdownAdapter::` classes. This will need to be done for any future use of `SmartdownAdapter` classes that share a name with top level classes, which is mostly smart_answer Presenters, as they're not namespaced into the `SmartAnswers` module, they probably should be.

For now this just fixes the instances breaking Smartdown flows in production, so we can continue testing. and  add a story to the Smartdown backlog to fix the broader name spacing issue.