Merge pull request #30 from colby-swandale/update-rubies

Update supported rubies to the latest version in travis

Author: hsbt

.travis.yml

@@ -1,9 +1,10 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.3.7
-  - 2.4.4
-  - 2.5.1
+  - 2.3.8
+  - 2.4.5
+  - 2.5.3
+  - 2.6.1
   - ruby-head
 script: rake test
 matrix: