Update gradlewrapper to gradle 1.11

OpenPGP-Keychain-API/build.gradle

@@ -1,3 +1,3 @@
 task wrapper(type: Wrapper) {
-    gradleVersion = '1.10'
-}
+    gradleVersion = '1.11'
+}

build.gradle

@@ -15,5 +15,5 @@ allprojects {
 }
 
 task wrapper(type: Wrapper) {
-    gradleVersion = '1.10'
+    gradleVersion = '1.11'
 }