Upgrade Travis to Ruby 2.3.1

Author: mattbrictson

.travis.yml

@@ -4,7 +4,7 @@ rvm:
   - 2.0
   - 2.1
   - 2.2
-  - 2.3.0
+  - 2.3.1
 gemfile:
   - gemfiles/4.0.gemfile
   - gemfiles/4.1.gemfile
@@ -20,7 +20,7 @@ matrix:
       gemfile: gemfiles/5.0.gemfile
   include:
     # Run Danger only once
-    - rvm: 2.3.0
+    - rvm: 2.3.1
       gemfile: gemfiles/5.0.gemfile
       script: bundle exec danger
 before_install: