.travis.yml in rmagick-2.16.0 vs .travis.yml in rmagick-3.0.0

@@ -1,70 +1,27 @@
 language: ruby
 
+cache:
+  directories:
+    - ~/.ccache
+
 os:
   - linux
 
 sudo: required
 
 env:
-  # Currently successful release
-  - IMAGEMAGICK_VERSION=6.6.9-10
-  # Ubuntu's current stable release
-  - IMAGEMAGICK_VERSION=6.7.7-10
-  # Latest 6.7 release
-  - IMAGEMAGICK_VERSION=6.7.9-10
-  # Latest 6.8 release
   - IMAGEMAGICK_VERSION=6.8.9-10
-  # Try with HDRI support, we don't mind if this fails currently.
   - IMAGEMAGICK_VERSION=6.8.9-10 CONFIGURE_OPTIONS=--enable-hdri
-  # Latest release
-  - IMAGEMAGICK_VERSION=latest
 
 before_install:
   - source before_install_$TRAVIS_OS_NAME.sh
 
 install: bundle install --verbose
 
 rvm:
-  - 1.8
-  - 1.9
-  - 2.0
-  - 2.1
-  - 2.2
-
-matrix:
-  exclude:
-    - rvm: 1.8
-      env: IMAGEMAGICK_VERSION=6.7.9-10
-    - rvm: 1.8
-      env: IMAGEMAGICK_VERSION=6.7.7-10
-    - rvm: 1.8
-      env: IMAGEMAGICK_VERSION=6.8.9-10 CONFIGURE_OPTIONS=--enable-hdri
-    - rvm: 1.8
-      env: IMAGEMAGICK_VERSION=6.8.9-10
-    - rvm: 1.9
-      env: IMAGEMAGICK_VERSION=6.7.9-10
-    - rvm: 1.9
-      env: IMAGEMAGICK_VERSION=6.8.9-10 CONFIGURE_OPTIONS=--enable-hdri
-    - rvm: 2.0
-      env: IMAGEMAGICK_VERSION=6.7.7-10
-    - rvm: 2.0
-      env: IMAGEMAGICK_VERSION=6.7.9-10
-    - rvm: 2.0
-      env: IMAGEMAGICK_VERSION=6.8.9-10
-    - rvm: 2.0
-      env: IMAGEMAGICK_VERSION=6.8.9-10 CONFIGURE_OPTIONS=--enable-hdri
-  allow_failures:
-    - env: IMAGEMAGICK_VERSION=6.7.7-10
-    - env: IMAGEMAGICK_VERSION=6.7.9-10
-      rvm: 2.1
-    - env: IMAGEMAGICK_VERSION=6.7.9-10
-      rvm: 2.2
-    - env: IMAGEMAGICK_VERSION=6.8.9-10
-      rvm: 2.1
-    - env: IMAGEMAGICK_VERSION=6.8.9-10 CONFIGURE_OPTIONS=--enable-hdri
-      rvm: 2.1
-    - env: IMAGEMAGICK_VERSION=latest
+  - 2.3
+  - 2.4
 
 notifications:
   webhooks:
     urls:
       - https://webhooks.gitter.im/e/a98c1112f5d60f97a532