Update .travis.yml

* Update rubies to latest version.
* Add ruby-head to Travis as allow_failures.
  * It's good to know new version Ruby's issue as faster before the release.
  * fast_finish is to get the Travis result as faster
    without waiting the result of the "allow_failures" items.
    See https://blog.travis-ci.com/2013-11-27-fast-finishing-builds/

Author: junaruga

.travis.yml

@@ -34,24 +34,24 @@ matrix:
       dist: trusty
       sudo: true
 
-    - rvm: 2.2.6
+    - rvm: 2.2.7
       env: EXECJS_RUNTIME=Node
-    - rvm: 2.2.6
+    - rvm: 2.2.7
       env: EXECJS_RUNTIME=Duktape
-    - rvm: 2.2.6
+    - rvm: 2.2.7
       env: EXECJS_RUNTIME=RubyRacer
-    - rvm: 2.2.6
+    - rvm: 2.2.7
       env: EXECJS_RUNTIME=MiniRacer
       dist: trusty
       sudo: true
 
-    - rvm: 2.3.3
+    - rvm: 2.3.4
       env: EXECJS_RUNTIME=Node
-    - rvm: 2.3.3
+    - rvm: 2.3.4
       env: EXECJS_RUNTIME=Duktape
-    - rvm: 2.3.3
+    - rvm: 2.3.4
       env: EXECJS_RUNTIME=RubyRacer
-    - rvm: 2.3.3
+    - rvm: 2.3.4
       env: EXECJS_RUNTIME=MiniRacer
       dist: trusty
       sudo: true
@@ -67,6 +67,17 @@ matrix:
       dist: trusty
       sudo: true
 
+    - rvm: ruby-head
+      env: EXECJS_RUNTIME=Node
+    - rvm: ruby-head
+      env: EXECJS_RUNTIME=Duktape
+    - rvm: ruby-head
+      env: EXECJS_RUNTIME=RubyRacer
+    - rvm: ruby-head
+      env: EXECJS_RUNTIME=MiniRacer
+      dist: trusty
+      sudo: true
+
     - rvm: jruby-19mode
       env: EXECJS_RUNTIME=Node
     - rvm: jruby-19mode
@@ -85,3 +96,6 @@ matrix:
     - os: osx
       env: EXECJS_RUNTIME=MiniRacer
       osx_image: xcode7.3
+  allow_failures:
+    - rvm: ruby-head
+  fast_finish: true