Add a function to return a node stack

[todo]

marvin/src/main/java/com/deflatedpickle/marvin/builder/Builder.java

Lines 9 to 14 in 34a9cb1

	// TODO: Add a function to return a node stack
	// TODO: Add a function to push a node to the stack
	public interface Builder<T> {
	/**
	* Finishes this builder
	* @return A builder, either this one or a new one

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This issue was generated by todo based on a TODO comment in 34a9cb1. It's been assigned to @DeflatedPickle because they committed the code.