Add a hash value access node and interpret it
Interpret array element access
Handle array index out of bounds in the interpreter
Make ASTs serializable
Support -u to dump ASTs on the command line
Begin testing directly against the tentative spec
Remove some leftover debug stuff
Add a few more AST dumps that already pass
Revert "Make ASTs serializable"

This reverts commit 659cfa17f755e2cd8e2ea66c851b0c9612625020.
Use a separate option to run through the AST serialization