feat(errors): show nicer errors if there are extra fields

Now you can see which field caused the error.

Author: bebraw

schema/validator.js

@@ -2,7 +2,9 @@ var Ajv = require('ajv');
 var ajv = new Ajv({allErrors: true});
 
 module.exports = function validate(schema, data) {
-	var ajv = new Ajv();
+	var ajv = new Ajv({
+		errorDataPath: 'property'
+	});
 	var isValid = ajv.validate(schema, data);
 
 	if(!isValid) {

test/extract.test.js

@@ -29,7 +29,7 @@ describe("ExtractTextPlugin.extract()", function() {
 					ExtractTextPlugin.extract({style: 'file.css'});
 				},
 				function(err) {
-					return err.message === 'data should NOT have additional properties';
+					return err.message === 'data[\'style\'] should NOT have additional properties';
 				}
 			);
 		});