Bump Gradle to 2.9

I'd do 2.10, the current stable, but the android plugin seems to break
with it.

.gitlab-ci.yml

@@ -19,9 +19,9 @@ before_script:
   - echo " == Installing Android emulator images"
   - echo y | android -s update sdk --no-ui -a -t android-10
   - echo " == Installing Gradle"
-  - wget -q -O gradle.zip https://services.gradle.org/distributions/gradle-2.8-bin.zip
+  - wget -q -O gradle.zip https://services.gradle.org/distributions/gradle-2.9-bin.zip
   - unzip -q gradle.zip
-  - export PATH="$PWD/gradle-2.8/bin:$PATH"
+  - export PATH="$PWD/gradle-2.9/bin:$PATH"
 
 test:
   script:

README.md

@@ -8,7 +8,7 @@ for Android.
 ## Building with Gradle
 
 The only requirements are the [Android SDK](https://developer.android.com/sdk/)
-and [Gradle](http://gradle.org/) 2.8:
+and [Gradle](http://gradle.org/) 2.9:
 
     cd F-Droid
     gradle assembleRelease

build.gradle

@@ -9,5 +9,5 @@ buildscript {
 }
 
 task wrapper(type: Wrapper) {
-    gradleVersion = '2.8'
+    gradleVersion = '2.9'
 }