.travis.yml in letter_opener_web-1.3.2 vs .travis.yml in letter_opener_web-1.3.3

@@ -1,10 +1,12 @@
 sudo: false
 language: ruby
 
 rvm:
-  - 2.3.3
-  - 2.2.6
+  - 2.5.0
+  - 2.4.3
+  - 2.3.6
+  - 2.2.9
   - 2.1.10
 
 cache: bundler
 
 before_install: