Update Ruby version

ndbroadbent · ndbroadbent · commit fbc7a45ffdbe · 2018-12-11T17:44:30.000+07:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,10 +1,7 @@
 language: ruby
 rvm:
   - 2.1.1
-  - 2.2.2
-notifications:
-  recipients:
-    - ricn@rny.io
+  - 2.5.3
 before_install:
   - sudo apt-get update -qq
   - sudo apt-get install libreoffice
