ref: 8fde6e4845eeafe6ffc4179218a3ac9e8049c0e6
dir: /TODO/
1) Add a repl 2) Figure out how to print the final bindings after running a query 3) Stop comparing strings all the time 4) Stop copying the entire goal stack into every choicepoint 5) Stop creating choicepoints when it is not needed 6) How to implement builtins nicely?