Enhancement: Cache dependencies between builds

Author: localheinz

.travis.yml

@@ -5,11 +5,15 @@ services:
 
 env:
   global:
-    - MEMCACHE_HOST=127.0.0.1 
+    - MEMCACHE_HOST=127.0.0.1
     - MEMCACHE_PORT=11211
 
 sudo: false
 
+cache:
+  directories:
+    - $HOME/.composer/cache
+
 php:
   # Can't test against 5.2; openssl is not available:
   # http://docs.travis-ci.com/user/languages/php/#PHP-installation