Update spark version in banner to 2.2.0

Author: foxish

src/jekyll/_config.yml

@@ -16,8 +16,8 @@ include:
 
 # These allow the documentation to be updated with newer releases
 # of Spark, Scala, and Mesos.
-SPARK_VERSION: 2.1.0-SNAPSHOT
-SPARK_VERSION_SHORT: 2.1.0
+SPARK_VERSION: 2.2.0-SNAPSHOT
+SPARK_VERSION_SHORT: 2.2.0
 SCALA_BINARY_VERSION: "2.11"
 SCALA_VERSION: "2.11.8"
 SPARK_ISSUE_TRACKER_URL: https://issues.apache.org/jira/browse/SPARK