Merge pull request #851 from TebbeUbben/dev

Improve Travis build speed by storing build cache

.travis.yml

@@ -21,4 +21,14 @@ script:
   - ./gradlew -Pcoverage testFullDebugUnitTest jacocoTestFullDebugUnitTestReport
 
 after_success:
-  - bash <(curl -s https://codecov.io/bash)
+  - bash <(curl -s https://codecov.io/bash)
+
+before_cache:
+  - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
+  - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
+
+cache:
+  directories:
+    - $HOME/.gradle/caches/
+    - $HOME/.gradle/wrapper/
+    - $HOME/.android/build-cache