Merge pull request #71 from nicolasleger/patch-1

[CI] Test against Ruby 2.5

Author: rafaelfranca

Diff for: .travis.yml

@@ -6,14 +6,16 @@ rvm:
   - 1.9.3
   - 2.0.0
   - 2.1.10
-  - 2.2.6
-  - 2.3.3
-  - 2.4.0
+  - 2.2.9
+  - 2.3.6
+  - 2.4.3
+  - 2.5.0
   - ruby-head
   - jruby
 matrix:
   fast_finish: true
   allow_failures:
+  - rvm: ruby-head
   - rvm: jruby
 notifications:
   email: false