hacked in a simple decision table fixture

This simple fixture will work with a very simple interface for:
```std::map<std::string, std::string> evaluate(std::map<std::string, std::string> inputs)```
interface cleanup for new DecisionFixture<T> class
Merge pull request #1 from AIM360/Kosta/simple_decision_fixture

added new and simple interface for doing decision table validations