Typeless field support

[aminya]

Adds support for typeless field

# x is a typeless field
@class Cat begin
    x
end

Also, makes the script detect the fields instead of using try-catch.

[aminya]

@rjplevin Could you take a look at my pull requests? They are tested. 😉

[rjplevin]

I'm doing so now. Thanks for the improvements!

[aminya]

You're welcome!