Bump gradle version.

build.gradle

@@ -18,6 +18,6 @@ apply from: 'javadoc.gradle'
 
 task createWrapper(type: Wrapper) {
     description 'Downloads and installs an up-to-date wrapper for gradle.'
-    gradleVersion = '2.1'
+    gradleVersion = '2.2.1'
 }
 

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Fri Sep 19 16:53:14 BST 2014
+#Thu Nov 27 00:24:26 GMT 2014
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=http\://services.gradle.org/distributions/gradle-2.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-2.2.1-bin.zip