Add zend-opcache module recipe

Also fix a bug when installing PHP: make sure PHP config dir exists
This is the offending code found in `php` recipe:
```
template "#{node['php']['conf_dir']}/php.ini" do
  source "php.ini.erb"
  owner "root"
  group "root"
  mode "0644"
end
```
So the problem is that `php` recipe runs this before `php::fpm` runs (which installs `php5-fpm` package that creates `/etc/php5/fpm`. The solution is either:
- To put `php::fpm` before `php` in each project's run list. (tested to work on precise32)
- To explicitly create the conf dir in `php` recipe (what I did above)

What's your call?