Update wrapper to 2.2

Change-Id: I394a1a792eea31cf531aaff74145848cdf47811d
diff --git a/wrapper/gradle-wrapper.properties b/wrapper/gradle-wrapper.properties
index 4f017a2..bc6c615 100644
--- a/wrapper/gradle-wrapper.properties
+++ b/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=../../external/gradle/gradle-2.1-bin.zip
+distributionUrl=../../external/gradle/gradle-2.2-bin.zip