.travis.yml in mb_string-0.1.2 vs .travis.yml in mb_string-0.1.3

@@ -1,4 +1,6 @@
 language: ruby
 rvm:
+  - 2.0.0
+  - 2.1.7
   - 2.2.3
 before_install: gem install bundler -v 1.10.6