.travis.yml in active_shipping-1.7.2 vs .travis.yml in active_shipping-1.7.3

@@ -4,9 +4,10 @@
 
 rvm:
 - "2.0"
 - "2.1"
 - "2.2"
+- "2.3.1"
 
 gemfile:
 - Gemfile.activesupport32
 - Gemfile.activesupport40
 - Gemfile.activesupport41