Fix typo in the Spark Job Main class

The main class of the Spark Job is Main and needs to be specified
with its full package name on the spark-submit CLI

Change-Id: I94f68979587fb5ed2958fbad06a21610ff0dd023
diff --git a/README.md b/README.md
index 2d9c25e..5a02ca3 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@
 
 ```bash
 bin/spark-submit \
-    --class com.gerritforge.analytics.gitcommits.job \
+    --class com.gerritforge.analytics.gitcommits.job.Main \
     --conf spark.es.nodes=es.mycompany.com \
     $JARS/analytics-etl.jar \
     --since 2000-06-01 \