a better travis

.travis.yml

@@ -1,15 +1,29 @@
+# whitelist
+branches:
+  only:
+    - wporg
+
 language: php
 
 php:
   - 5.2
   - 5.3
   - 5.4
   - 5.5
+  - 5.6
+
+sudo: false
+
+cache:
+- bundler
+- apt
+
+addons:
+  apt:
+    packages:
+    - ruby
 
-before_script:
-  - sudo apt-get install ruby
-  - gem install nyx
+install: gem install nyx
 
 script:
-  - nyx version
-  - nyx check:php .
+    - nyx check:php .