depend on concourse-config instead of config-framework

Change-Id: Ie64adb6011791afa8cfdb86efa19800d9e90e4b0
force subclass to implement a constructor

Change-Id: I2bd760af2d685aa4049609b84fa87bd2acf4a83f
update README

Change-Id: Ifabf960c7aeae3737ee8255a3467686f996d3559