Add coursier cache to CI

These locations are taken from https://get-coursier.io/docs/cache.

.appveyor.yml

@@ -26,5 +26,6 @@ test_script:
   - sbt "scripted actions/* classloader-cache/* nio/* watch/*" "testOnly sbt.ServerSpec"
 
 cache:
+  - '%LOCALAPPDATA%\Coursier\Cache\v1'
   - '%USERPROFILE%\.ivy2\cache'
   - '%USERPROFILE%\.sbt'

.travis.yml

@@ -36,11 +36,13 @@ script:
   - sbt -Dsbt.ci=true -J-XX:ReservedCodeCacheSize=128m -J-Xmx800M -J-Xms800M -J-server "$SBT_CMD"
 
 before_cache:
-  - find $HOME/.ivy2 -name "ivydata-*.properties" -delete
-  - find $HOME/.sbt  -name "*.lock"               -delete
+  - find $HOME/.cache/coursier/v1 -name "ivydata-*.properties" -delete
+  - find $HOME/.ivy2              -name "ivydata-*.properties" -delete
+  - find $HOME/.sbt               -name "*.lock"               -delete
 
 cache:
   directories:
+    - $HOME/.cache/coursier/v1
     - $HOME/.ivy2/cache
     - $HOME/.sbt/boot
     - $HOME/.jabba