Merge pull request #79 from derekwaynecarr/install_broker_cartridges

Add command to setup broker data for geard
Added 'install_geard_images' to pull the cartridge images from Docker index
Merge pull request #77 from mfojtik/install_geard_Images

Added install_geard_images task and added 'centos' to list of default Docker images.
Install rhc in vagrant user gem env