Update README.md

Add buttons to docs

Author: yemel

README.md

@@ -4,8 +4,7 @@
 [![Build Status](https://img.shields.io/travis/bitpay/bitcore.svg?branch=master&style=flat-square)](https://travis-ci.org/bitpay/bitcore)
 [![Coverage Status](https://img.shields.io/coveralls/bitpay/bitcore.svg?style=flat-square)](https://coveralls.io/r/bitpay/bitcore)
 
-[Read the Developer Guide](https://bitpay.github.io/bitcore/docs/#!index.md).
-[Read the API Reference](https://bitpay.github.io/bitcore/apiref).
+[![Read the Developer Guide](http://bitpay.github.io/bitcore/images/read-the-developer-guide-btn.png)](https://bitpay.github.io/bitcore/docs/#!index.md)  [![Read the API Reference](http://bitpay.github.io/bitcore/images/read-the-api-reference-btn.png)](https://bitpay.github.io/bitcore/apiref)
 
 
 A pure and simple javascript bitcoin API.