Use cache for Travis

And also avoid Github api limit

.travis.yml

@@ -17,10 +17,17 @@ matrix:
 # faster builds on new travis setup not using sudo
 sudo: false
 
+# cache vendor dirs
+cache:
+    directories:
+        - vendor
+        - $HOME/.composer/cache
+
 install:
     - composer self-update
 
 before_script:
+    - if [ -n "$GH_TOKEN" ]; then composer config github-oauth.github.com ${GH_TOKEN}; fi;
     # disable TLS for composer because openssl is disabled for PHP 5.3.3 on travis
     # see: https://blog.travis-ci.com/upcoming_ubuntu_11_10_migration/
     - if [[ $TRAVIS_PHP_VERSION = 5.3.3 ]]; then composer config -g -- disable-tls true; fi;