ParametersParser refacor

WIP
> Shouldn't this be considered as description node? Why are we processing it as unexpected node?

This is good point! The only reason for this would be to warn user about the mistake. It is quite annoying when you think you wrote a keyword and it ends up (without warning) in the description.

However this should be handled more conceptually. So while leaving this to on the parser will for not worsen the situation for writer, I agree. 

We should address this in #65