Return self(this) with each : ability to chain methods

this allows chaining actions on map

    let fields = HashMap()
	:add("firstName", "Bob")
	:add("lastName", "Morane")
	:add("age", 42)


    fields:each(|key, value|-> println(key +" : "+ value))
        :add("firstName","John")
        :add("lastName","Doe")
        :each(|key, value|-> println(key +" : "+ value))