Switch case fall through

I implemented the switch case fall through.
I would like some feedback (about the code but maybe also missing cases?)

 I believe it works pretty good, I've changed it to only use the visitSwatchStatement function because it didn't really work when I used the visitCaseSwitchClause and visitDefaultSwitchClause functions. Mostly because of nesting issues and because I needed to know if the rule above had a break statement.

Edit: when accepted, this would fix #136 
update README too :)