Ruby

Add graphviz output

This adds a method to blocks to get outgoing ids, then uses the outgoing
ids to generate a graphviz graph. Two methods were added to the Block
object. One method returns an id for the block, which is just the
address of the underlying block. The other method returns a list of
outgoing block ids. We can use Block#id in conjunction with
Block#outgoing_ids to construct a graph of blocks