Let memcached::installer-source recipe build

- Added more specs for memcached::installer-source
  recipe in order to have a successful build process.
- Added --format parameter in .rspec config file
- Added test-kitchen verify support for centos-6.5
  Note: memcached::installer-source strictly rely on a
        CentOS-6.5 machine. It's not guaranteed that the
        recipe will work on other OSes given the current
        codebase.
- Added TODO file to have a reference for future development :)
Merge branch 'feature/20140831-let-installation-source-recipe-work' into develop