.travis.yml in knapsack-1.8.0 vs .travis.yml in knapsack-1.9.0

@@ -6,9 +6,10 @@
   - 2.1.5
   - 2.2.0
   - 2.2.2
   - 2.2.3
   - 2.3.0
+  - 2.3.1
 addons:
   code_climate:
     repo_token: 38686058eed480dd0fcf8bce9015733e0bae88e44e30f4a1ac63df8aec2f86d8
 before_install:
   - "echo 'gem: --no-ri --no-rdoc' > ~/.gemrc"