add standard badge

Author: dcousens

readme.markdown renamed to README.md

@@ -3,6 +3,7 @@
 A port of node's `crypto` module to the browser.
 
 [![travis](https://img.shields.io/travis/crypto-browserify/crypto-browserify/master.svg?style=flat)](https://travis-ci.org/crypto-browserify/crypto-browserify)
+[![js-standard-style](https://cdn.rawgit.com/feross/standard/master/badge.svg)](https://github.com/feross/standard)
 
 The goal of this module is to reimplement node's crypto module,
 in pure javascript so that it can run in the browser.