Only call getEffectiveDefaults when needed

The call to `getEffectiveDefaults` will make `json-smart` dependency
required for processing.  By removing the call when not needed
`json-smart` can be safely excluded.

In addition the logger was removed since it was not being used.

json-path/src/main/java/com/jayway/jsonpath/Configuration.java

@@ -18,9 +18,6 @@ import com.jayway.jsonpath.internal.DefaultsImpl;
 import com.jayway.jsonpath.spi.json.JsonProvider;
 import com.jayway.jsonpath.spi.mapper.MappingProvider;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -36,8 +33,6 @@ import static java.util.Arrays.asList;
  */
 public class Configuration {
 
-    private static final Logger logger = LoggerFactory.getLogger(Configuration.class);
-
     private static Defaults DEFAULTS = null;
 
     /**
@@ -230,13 +225,15 @@ public class Configuration {
         }
 
         public Configuration build() {
-            Defaults defaults = getEffectiveDefaults();
+            if (jsonProvider == null || mappingProvider == null) {
+                final Defaults defaults = getEffectiveDefaults();
                 if (jsonProvider == null) {
                     jsonProvider = defaults.jsonProvider();
                 }
                 if (mappingProvider == null){
                     mappingProvider = defaults.mappingProvider();
                 }
+            }
             return new Configuration(jsonProvider, mappingProvider, options, evaluationListener);
         }
     }