speed up Travis builds using caching feature

Author: gourlaysama

.travis.yml

@@ -26,3 +26,12 @@ notifications:
   email:
     - adriaan.moors@typesafe.com
     - antoine@gourlay.fr
+
+before_cache:
+  - find $HOME/.sbt -name "*.lock" | xargs rm
+  - find $HOME/.ivy2/cache -name "ivydata-*.properties" | xargs rm
+cache:
+  directories:
+  - $HOME/.ivy2/cache
+  - $HOME/.sbt/boot
+  - $HOME/.sbt/launchers