Add a new module for apcu installation

"PHP APCu is now included in the repository for both PHP 5.4 and 5.5. APCu is a cut down version of APC, which just deals with user cache, removing it’s opcode cache that doesn’t support PHP 5.5."
Update metadata.rb to refer new module_apcu recipe
Merge pull request #4 from Restless-ET/feature/add-module_apcu

Feature/add module apcu