added installation instructions for modman
added installation instructions for modman

caciobanu/improved-magento-layered-navigation,Militree/improved-magento-layered-navigation,caciobanu/improved-magento-layered-navigation,Militree/improved-magento-layered-navigation,caciobanu/improved-magento-layered-navigation,Militree/improved-magento-layered-navigation