Update CONTRIBUTING.md
Update CONTRIBUTING.md

Use new link for Concourse Developer Setup guide
cinchapi/concourse,hcuffy/concourse,kylycht/concourse,kylycht/concourse,dubex/concourse,JerJohn15/concourse,remiemalik/concourse,vrnithinkumar/concourse,vrnithinkumar/concourse,vrnithinkumar/concourse,remiemalik/concourse,hcuffy/concourse,vrnithinkumar/concourse,JerJohn15/concourse,remiemalik/concourse,kylycht/concourse,JerJohn15/concourse,cinchapi/concourse,dubex/concourse,hcuffy/concourse,JerJohn15/concourse,cinchapi/concourse,cinchapi/concourse,JerJohn15/concourse,hcuffy/concourse,cinchapi/concourse,hcuffy/concourse,vrnithinkumar/concourse,JerJohn15/concourse,remiemalik/concourse,vrnithinkumar/concourse,remiemalik/concourse,dubex/concourse,kylycht/concourse,dubex/concourse,hcuffy/concourse,cinchapi/concourse,kylycht/concourse,dubex/concourse,kylycht/concourse,remiemalik/concourse,dubex/concourse