gradle caching stuff for travis

.travis.yml

@@ -1,2 +1,10 @@
 language: java
 before_script: cd workspace/gradle
+
+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/