Update vagrant basebox to CentOS 6.4 and update cookbooks.

Updating to CentOS 6.4 will fix missing haproxy package since it got
removed from EPEL and is now part of the default repo.

Cookbook updates mainly involve newer rbenv and nginx/passenger
recipes.

Add missing cookbook dependencies now required under chef-solo 11.
Bump other cookbooks to latest versions.
Add and update missing cookbooks.
Update rubygems cookbook.