Merge pull request #163 from nijikon/update-to-recent-version

update to recent versions in travis

.travis.yml

@@ -9,17 +9,24 @@ branches:
     - master
 
 rvm:
-  - jruby-9.1.6.0
-  - 2.2.6
-  - 2.3.3
-  - 2.4.0
+  - 2.2.8
+  - 2.3.5
+  - 2.4.2
+  - ruby-head
+  - jruby-9.1.14.0
+  - jruby-head
+  - rbx-2
 
 env:
   - LIBSODIUM_VERSION=1.0.0  # Minimum supported
   - LIBSODIUM_VERSION=1.0.11 # Latest released
 
 matrix:
   fast_finish: true
+  allow_failures:
+    - rvm: ruby-head
+    - rvm: jruby-head
+    - rvm: rbx-2
 
 notifications:
   irc: "irc.freenode.org#cryptosphere"