fix(docs): Correct url and not for gradle (#158)

Author: Michael Brewer

example/README.md

@@ -26,7 +26,7 @@ To use the SAM CLI, you need the following tools.
 * SAM CLI - [Install the SAM CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install.html)
 * Java8 - [Install the Java SE Development Kit 8](http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html)
 * Maven - [Install Maven](https://maven.apache.org/install.html) or
-* Gradle - [Install Maven](https://maven.apache.org/install.html)
+* Gradle - [Install Gradle](https://gradle.org/install/)
 * Docker - [Install Docker community edition](https://hub.docker.com/search/?type=edition&offering=community)
 
 To build and deploy your application for the first time, run the following in your shell: