Merge pull request #6 from marshall-lee/fix_travis_rubies

Add MRI 2.2 and 2.3, fix 2.0 and 2.1 to use latest.

.travis.yml

@@ -3,12 +3,15 @@ bundler_args: --without development
 before_install: gem install bundler
 rvm:
   - 1.9.3
-  - 2.0.0
-  - 2.1.5
+  - 2.0
+  - 2.1
+  - 2.2
+  - 2.3.0
   - ruby-head
-  - jruby
+  - jruby-head
   - rbx
 matrix:
   allow_failures:
     - rvm: rbx
-    - rvm: jruby
+    - rvm: jruby-head
+    - rvm: ruby-head