Update README.markdown

README.markdown

@@ -156,7 +156,12 @@ Package [Production URL](https://login.salesforce.com/packaging/installPackage.a
 Installing the Source Code (Developers)
 =======================================
 
-If you are a developer obtain the source code from this repository if you wish to develop it further and/or contribute to it. Click [Deploy to Salesforce](https://githubsfdeploy.herokuapp.com/app/githubdeploy/afawcett/declarative-lookup-rollup-summaries) to deploy the source code to your developer org.
+If you are a developer obtain the source code from this repository if you wish to develop it further and/or contribute to it. Click the button below to deploy the source code to your developer or sandbox org.
+
+<a href="https://githubsfdeploy.herokuapp.com?owner=afawcett&repo=declarative-lookup-rollup-summaries">
+  <img alt="Deploy to Salesforce"
+       src="https://raw.githubusercontent.com/afawcett/githubsfdeploy/master/src/main/webapp/resources/img/deploy.png">
+</a>
 
 **KNOWN INSTALL ISSUE** Sometimes the Permission Set files will not deploy, based on org differences, such as features enabled. If you encounter this problem, Clone the repo manually and use your IDE or Ant script to deploy without the Permission Sets. I will be looking into fixing this [issue](https://github.com/afawcett/declarative-lookup-rollup-summaries/issues/58) in the future.