improve materialize performance
Materialize was relying on removing black listed and non-white listed codes from value sets.  This required cloning the value set.  This changes the code to pick the appropriate code during code selection without modifying the value set model.  Removing the requirement to clone improves the performance by 5x
fix tests for patient builder by turning hash into SVS valueset object
Merge pull request #20 from projecttacoma/improve_materialize_performance

improve materialize performance