Modernize rubies

Author: pschambacher

.travis.yml

@@ -5,18 +5,16 @@ sudo: false
 branches:
   only: master
 rvm:
-  - 2.0.0
-  - 2.1.8
-  - 2.2.4
+  - 2.2.7
+  - 2.3.4
+  - 2.4.1
 gemfile:
   - gemfiles/rails_3.2.gemfile
   - gemfiles/rails_4.2.gemfile
   - gemfiles/rails_5.0.gemfile
 matrix:
   exclude:
-    - rvm: 2.0.0
-      gemfile: gemfiles/rails_5.0.gemfile
-    - rvm: 2.1.8
-      gemfile: gemfiles/rails_5.0.gemfile
-    - rvm: 2.2.4
+    - rvm: 2.4.1
       gemfile: gemfiles/rails_3.2.gemfile
+    - rvm: 2.4.1
+      gemfile: gemfiles/rails_4.2.gemfile