Add Spark 2.2 to travis build #60

Add Spark 2.2 to travis build

Author: jkbradley

.travis.yml

@@ -9,6 +9,7 @@ cache:
 env:
   matrix:
     - SPARK_VERSION="2.1.1" SPARK_BUILD="spark-$SPARK_VERSION-bin-hadoop2.7" SPARK_BUILD_URL="http://d3kbcqa49mib13.cloudfront.net/$SPARK_BUILD.tgz"
+    - SPARK_VERSION="2.2.0" SPARK_BUILD="spark-$SPARK_VERSION-bin-hadoop2.7" SPARK_BUILD_URL="http://d3kbcqa49mib13.cloudfront.net/$SPARK_BUILD.tgz"
 
 before_install:
  - ./bin/download_travis_dependencies.sh