readme: Update images, gh-pages branch was deleted

README.md

@@ -32,7 +32,9 @@ simpleTx.sign(privateKey);
 
 The complete docs are hosted here: [bitcore documentation](http://bitcore.io/guide/). There's also a [bitcore API reference](http://bitcore.io/api/) available generated from the JSDocs of the project, where you'll find low-level details on each bitcore utility.
 
-[![Read the Developer Guide](http://bitpay.github.io/bitcore/images/read-the-developer-guide-btn.png)](http://bitcore.io/guide/)  [![Read the API Reference](http://bitpay.github.io/bitcore/images/read-the-api-reference-btn.png)](http://bitcore.io/api/)
+[Read the Developer Guide](http://bitcore.io/guide/)
+
+[Read the API Reference](http://bitcore.io/api/)
 
 To get community assistance and ask for help with implementation questions, please use our [community forums](http://bitpaylabs.com/c/bitcore).