Add Grunt example.

example/Gruntfile.js

@@ -0,0 +1,26 @@
+"use strict";
+
+var markdownlint = require("../lib/markdownlint");
+
+module.exports = function wrapper(grunt) {
+  grunt.initConfig({
+    "markdownlint": {
+      "example": {
+        "src": [ "*.md" ]
+      }
+    }
+  });
+
+  grunt.registerMultiTask("markdownlint", function task() {
+    var done = this.async();
+    markdownlint(
+      { "files": this.filesSrc },
+      function callback(err, result) {
+        var resultString = err || ((result || "").toString());
+        if (resultString) {
+          grunt.fail.warn("\n" + resultString + "\n");
+        }
+        done(!err || !resultString);
+      });
+  });
+};