Defer to phpcs.xml file if present.

- Fixes #311

Author: jhedstrom

tasks/quality.js

@@ -190,12 +190,20 @@ module.exports = function(grunt) {
   grunt.registerTask('validate', 'Validate the quality of custom code.', function(mode) {
     phpcsConfig = grunt.config.get('phpcs');
     var files;
+
     if (phpcsConfig && phpcsConfig.validate) {
-      files = filesToProcess(phpcsConfig.validate.src);
-      if (files.length) {
-        grunt.config.set('phpcs.validate.src', files);
+      // Defer to phpcs.xml/phpcs.xml.dist if present.
+      if (grunt.file.exists('./phpcs.xml') || grunt.file.exists('./phpcs.xml.dist')) {
+        grunt.config.set('phpcs.validate.src', []);
         validate.push('phpcs:validate');
       }
+      else {
+        files = filesToProcess(phpcsConfig.validate.src);
+        if (files.length) {
+          grunt.config.set('phpcs.validate.src', files);
+          validate.push('phpcs:validate');
+        }
+      }
     }
     eslintConfig = grunt.config.get('eslint');
     var eslintIgnoreError = grunt.config.get('config.validate.ignoreError') === undefined ? false : grunt.config.get('config.validate.ignoreError');