Issue 55 fix reserved identifiers

[Jastrzebowski]

Describe your changes

I'm fixing an issue where the reserved identifiers are incorrectly found in the if forming part of an identifier, for example, for in form. I couldn't find a good way to allow reserved words as stand-alone identifiers, like for.property, so I moved the reserved words handling to the visitor, which is better aware of the context where the reserved word is used.

Issue ticket number/link

#55

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [X] I have added tests (if possible)
• [ ] I have updated the readme (if necessary)
• [ ] I have updated the demo (if necessary)