Add a preCondition callback to SuccessCriteria object

The preCondition callback will be executed during the call to
SuccessCriteria.registerTests() and replace the testCollection sent with an
empty testCollection.
Add a preCondition callback to SuccessCriteria object

The preCondition callback will be executed during the call to
SuccessCriteria.registerTests() and replace the testCollection sent with an
empty testCollection.
Merge pull request #253 from theodoreb/preEvaluator

Add a preEvaluator callback to SuccessCriteria object