trim down travis combinations

Author: rmosolgo

.travis.yml

@@ -3,7 +3,6 @@ sudo: false
 cache: bundler
 rvm:
   - 2.3.0
-  - 2.2.4
   - 2.1
   - jruby-9.0.1.0
 
@@ -18,9 +17,21 @@ gemfile:
 
 matrix:
   fast_finish: true
-  exclude:
-    - gemfile: gemfiles/rails_5.gemfile
-      rvm: 2.1
+  include:
+    - rvm: 2.1
+      gemfile: gemfiles/rails_3.2.gemfile
+    - rvm: 2.1
+      gemfile: gemfiles/rails_4.0.gemfile
+    - rvm: 2.1
+      gemfile: gemfiles/rails_4.1.gemfile
+    - rvm: 2.1
+      gemfile: gemfiles/rails_4.2_sprockets_3.gemfile
+    - rvm: jruby-9.0.1.0
+      gemfile: gemfiles/rails_3.2.gemfile
+    - rvm: jruby-9.0.1.0
+      gemfile: gemfiles/rails_4.2_sprockets_3.gemfile
+    - rvm: jruby-9.0.1.0
+      gemfile: gemfiles/rails_5.gemfile
   allow_failures:
     - rvm: jruby-9.0.1.0