Always validate that all the nodes of the graph exist.
This helped find some other holes in this logic.
Merge pull request #32 from Obvious/nick-fixit

Always validate that all nodes of the graph exist
Added fix for using the same .builds() twice in a node
Added fix for using the same .builds() twice in a node
Removing double compile test because it doesnt fail currently
Added checking for missing 'args.' refs
Removing test which has been replaced by newer tests