Add Prerequisite to Java Tutorial

docs/java-tutorial.md

@@ -2,6 +2,11 @@
 
 #### Running The Example
 
+**_Install the serverless framework_**
+```shell
+npm install serverless -g
+```
+
 **_Use shell commands to clone the repository and change the working directory to the Java example_**
 ```shell
 git clone [email protected]:blackboard/lambda-selenium.git
@@ -32,4 +37,4 @@ gradle clean test
 
 When the tests are ran, they will be executed in parallel by invoking the Lambda function that was created.
 Once the tests are complete, open folder './build/screenshots' to view screenshots taken inside the running tests.
-If a test fails, the exception will be thrown for the test case and logged to the console.
+If a test fails, the exception will be thrown for the test case and logged to the console.