.travis.yml in closure_tree-6.5.0 vs .travis.yml in closure_tree-6.6.0

@@ -2,18 +2,18 @@
 sudo: false
 language: ruby
 rvm:
   - 2.4.0
   - 2.3.3
-  - 2.2.6
+  - 2.2.7
 # these haven't been passing for a while:
 #  - jruby-head
 #  - rbx
 
 gemfile:
-  - gemfiles/activerecord_4.2.gemfile
-  - gemfiles/activerecord_5.0_foreigner.gemfile
+  - gemfiles/activerecord_5.1.gemfile
   - gemfiles/activerecord_5.0.gemfile
+  - gemfiles/activerecord_4.2.gemfile
   - gemfiles/activerecord_edge.gemfile
 
 env:
   - DB=sqlite
   - DB=mysql