.travis.yml in litecable-0.5.0 vs .travis.yml in litecable-0.6.0

@@ -1,7 +1,16 @@
+sudo: false
 language: ruby
 cache: bundler
 
+before_install:
+  - gem update --system
+  - gem install bundler -v '< 2'
+
 matrix:
   include:
-    - rvm: 2.3.3
-    - rvm: 2.4.0
+    - rvm: 2.4
+    - rvm: 2.5
+    - rvm: 2.6
+    - rvm: ruby-head
+  allow_failures:
+    - rvm: ruby-head