Update Gradle version

Author: xsveda

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
-#Wed Feb 04 20:10:55 CET 2015
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.2.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-3.1-all.zip