CI against ruby 2.4.0

And skip testing rails 4.2 x ruby 2.4, 2.5

Author: amatsuda

.travis.yml

@@ -6,6 +6,7 @@ rvm:
   - 2.1.10
   - 2.2.5
   - 2.3.1
+  - 2.4.0
   - jruby
   - ruby-head
 gemfile:
@@ -22,6 +23,10 @@ matrix:
       gemfile: gemfiles/active_support_5.0.gemfile
     - rvm: 2.1.10
       gemfile: gemfiles/active_support_5.0.gemfile
+    - rvm: 2.4.0
+      gemfile: gemfiles/active_support_4.2.gemfile
+    - rvm: ruby-head
+      gemfile: gemfiles/active_support_4.2.gemfile
     - rvm: jruby
       gemfile: gemfiles/active_support_5.0.gemfile
 notifications: