update travis cache settings (#2158)

mostly copied from circe

.travis.yml

@@ -58,14 +58,6 @@ env:
 
 cache:
   directories:
-  - $HOME/.sbt/1.1/dependency
-  - $HOME/.sbt/boot/scala*
-  - $HOME/.sbt/launchers
-  - $HOME/.ivy2/cache
-  - $HOME/.nvm
-
-before_cache:
-  - du -h -d 1 $HOME/.ivy2/cache
-  - du -h -d 2 $HOME/.sbt/
-  - find $HOME/.sbt -name "*.lock" -type f -delete
-  - find $HOME/.ivy2/cache -name "ivydata-*.properties" -type f -delete
+    - $HOME/.ivy2/cache
+    - $HOME/.sbt/boot
+    - $HOME/.coursier