travis: bump ruby

.travis.yml

@@ -3,12 +3,15 @@ language: ruby
 sudo: true # need this for libgirepository1.0-dev
 # sudo: false # taking advantage of container-based infrastructure
 # cache: bundler # cache bundled gems from build to build
-
+addons:
+  apt:
+    packages:
+      - libgirepository1.0-dev # for gobject-introspection
 rvm:
   - 2.2
   - 2.3.2
   - 2.3.3
-  - 2.4.0
+  - 2.4.1
 matrix:
   allow_failures:
     - rvm: 2.3.3