Merge pull request #130 from 5apps/feature/more_rubies_specs

Run the specs on Ruby 2.5 and 2.6 too

.travis.yml

@@ -1,7 +1,9 @@
 language: ruby
 cache: bundler
 rvm:
-  - 2.4.1
+  - 2.4
+  - 2.5
+  - 2.6
 services:
   - redis-server
 before_script: