Merge pull request #107 from skunkworker/add_ruby_2_6

Added Ruby 2.6 and bumped to 2.3.8, 2.4.5 and 2.5.3

Author: bolandrm

.travis.yml

@@ -3,8 +3,9 @@ language: ruby
 bundler_args: "--binstubs --standalone --without documentation --path ../bundle"
 script: "bundle exec rake test"
 rvm:
-  - 2.3.7
-  - 2.4.4
-  - 2.5.1
+  - 2.3.8
+  - 2.4.5
+  - 2.5.3
+  - 2.6.1
 notifications:
   email: false