Added minimum java version note to driver-async installation guide

Author: rozza

docs/reference/content/driver-async/getting-started/installation-guide.md

@@ -10,8 +10,13 @@ title = "Installation Guide"
 
 # Installation
 
+
 The recommended way to get started using one of the drivers in your project is with a dependency management system.
 
+{{% note class="important" %}}
+The MongoDB Async Driver requires Java 7 or greater.
+{{% /note %}}
+
 {{< distroPicker >}}
 
 ## MongoDB Async Driver