Initial dead code elimination work

[phated]

This is my initial work on dead code elimination for #22 - There's still tons of work/cleanup do be done on this logic.

[ian-harshman-ck]

Could add a hasFields property to the struct node to aid in this sort of logic

[phated]

I really like that idea. I could add a size property (as a getter) to each Node that has fields to know how big each one is. Thanks @ian-harshman-ck!