.travis.yml in pork-1.5.0 vs .travis.yml in pork-2.0.0

@@ -1,10 +1,9 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.1
-  - 2.2
-  - 2.3.0
+  - 2.2.5
+  - 2.3.1
   - rbx
   - jruby-9
 
 before_install:
   - rvm get head