Cache Travis dependencies

Author: nhaarman

.travis.yml

@@ -13,4 +13,15 @@ install:
  - true
 
 script:
-  - ./gradlew test
+  - ./gradlew test
+
+before_cache:
+  - rm -f $HOME/.gradle/caches/modules-2/modules-2.lock
+  - rm -f $HOME/.gradle/caches/2.10/plugin-resolution/cache.properties.lock
+  - rm -f $HOME/.gradle/caches/2.10/plugin-resolution/cache.properties
+cache:
+  directories:
+    - $HOME/.gradle/caches
+    - $HOME/.gradle/daemon
+    - $HOME/.gradle/native
+    - $HOME/.gradle/wrapper