added definitions for mkdirp

mkdirp/mkdirp-tests.ts

@@ -0,0 +1,16 @@
+/// <reference path="mkdirp.d.ts" />
+
+import mkdirp = require('mkdirp');
+
+var str: string;
+var num: number;
+
+mkdirp(str, num, (err, made) => {
+	str = made;
+});
+mkdirp(str, (err, made) => {
+	str = made;
+});
+
+str = mkdirp.sync(str, num);
+str = mkdirp.sync(str);