add database description in readme
add database description in readme

pradyutsarma/app-autoscaler,cloudfoundry-incubator/app-autoscaler,pradyutsarma/app-autoscaler,cloudfoundry-incubator/app-autoscaler,cloudfoundry-incubator/app-autoscaler,qibobo/app-autoscaler,qibobo/app-autoscaler,qibobo/app-autoscaler,florindragos/open-Autoscaler,pradyutsarma/app-autoscaler,florindragos/open-Autoscaler,florindragos/open-Autoscaler,qibobo/app-autoscaler,cfibmers/open-Autoscaler,pradyutsarma/app-autoscaler,cfibmers/open-Autoscaler,cfibmers/open-Autoscaler,cloudfoundry-incubator/app-autoscaler