.travis.yml in gimei-0.2.0 vs .travis.yml in gimei-0.3.0

@@ -1,6 +1,10 @@
 language: ruby
 rvm:
   - "1.9.3"
   - "2.0.0"
-  - "2.1.0"
-
+  - "2.1.10"
+  - "2.2.7"
+  - "2.3.4"
+  - "2.4.1"
+before_install:
+  - gem update bundler