Add destructuring to more places

[BobVarioa]

Fixes #122

Adds destructuring to:

• for..of
• for..in
• Assignment
• Function Arguments

The only other supported destructuring location (?) is try..catch's error but that's currently unimplemented.

(also >30% test262 completion 🎉, at least for me locally)

[CanadaHonk]

Looks good for the most part, thanks a lot! Just some nits/questions :)