Don't monkey patch/make real classes for types

`ext.rb` could be replaced with `types.rb` and do stuff like `class Lasp::List < Array` to get the same functionality and safely override `#call` etc. They could also give proper `LaspErrors` if `#chars` or `#to_i` is called on a list for example
- `Lasp::List < Array`
- `Lasp::Dict < Hash`
