public Builder environment (Environment aEnvironment) {
      environment = aEnvironment;
      return this;
    }
a {@link TaskEvaluator} implemenation which is based on 
Spring Expression Language for resolving expressions.

@author Arik Cohen
@since Mar 31, 2017
src/main/java/com/creactiviti/piper/core/task/SpelTaskEvaluator.java