Fix build instructions in README.md
Actually jetcd is built with `gradle` instead of `maven`
@@ -99,7 +99,7 @@ The current major version is zero (0.y.z). Anything may change at any time. The
## Build from source
-The project can be built with [Apache Maven](https://maven.apache.org/):
+The project can be built with [Gradle](https://gradle.org/):
```
./gradlew compileJava
