.travis.yml in slack-api-1.2.4 vs .travis.yml in slack-api-1.3.0

@@ -1,11 +1,26 @@
+language: ruby
+
 rvm:
   - 2.1.10
-  - 2.2.5
-  - 2.3.1
-  - jruby-9.1.2.0
+  - 2.2.6
+  - 2.3.3
+  - 2.4.0
+  - ruby-head
+  - jruby-9.1.7.0
+  - jruby-head
 
+matrix:
+  allow_failures:
+    - rvm: ruby-head
+    - rvm: jruby-9.1.7.0
+    - rvm: jruby-head
 git:
   submodules: false
 
 before_install:
+  - gem update --system
   - gem update bundler
+
+cache: bundler
+
+sudo: false