Module parsing

[theodorton]

Modules are currently not transpiled, as I haven't decided how they should be treated.

I believe the most natural way would be to treat a Crystal module as an Object, defined as a global.

module Foo
  module Bar
    def hello
      "world"
    end
  end
end

global.Foo = {
  Bar: {
    hello() { return "world"; },
  },
};