add 2.5.0 versions to travis

Author: viuginick1

.travis.yml

@@ -1,9 +1,18 @@
 language: ruby
+os:
+  - linux
+  - osx
 before_install:
   - gem install bundler
 rvm:
-  - ruby-head
   - 2.0.0
   - 2.1
   - 2.2
   - 2.3
+  - 2.5.0-preview1
+  - ruby-head
+
+matrix:
+  exclude:
+  - os: osx
+    rvm: 2.0.0