Fixes #183 Validation error when field is nullable and consumer sends in a null value

Author: ddobrin

src/main/java/com/networknt/schema/EnumValidator.java

@@ -52,7 +52,7 @@ public EnumValidator(String schemaPath, JsonNode schemaNode, JsonSchema parentSc
             }
 
             // check if the parent schema declares the fields as nullable
-            if(config.getHandleNullableField()) {
+            if(config.isHandleNullableField()) {
 	            JsonNode nullable = parentSchema.getSchemaNode().get("nullable");
 	            if (nullable != null && nullable.asBoolean()) {
 	            	nodes.add(NullNode.getInstance());

src/main/java/com/networknt/schema/SchemaValidatorsConfig.java

@@ -73,7 +73,7 @@ public void setMissingNodeAsError(boolean missingNodeAsError) {
     	this.missingNodeAsError = missingNodeAsError;
     }
 
-    public boolean getHandleNullableField() {
+    public boolean isHandleNullableField() {
 		return handleNullableField;
 	}