.travis.yml in mida-0.3.9 vs .travis.yml in mida-0.4.0

- old
+ new

@@ -1,8 +1,13 @@
 language: ruby
+sudo: false
+cache:
+  bundler: true
 rvm:
-  - 1.9.2
-  - 1.9.3
-  - 2.0.0
+  - 2.2.4
+  - 2.3.0
 branches:
   only:
     - master
+env:
+  global:
+    - NOKOGIRI_USE_SYSTEM_LIBRARIES=true