Update CONTRIBUTING.md
Update CONTRIBUTING.md

It pointed to the repo in heroku's organization, but it is hosted in interagent now
shopkeep/prmd,mlr/prmd,uberjay/prmd,MobileDevHQ/prmd,IceDragon200/prmd,mlr/prmd,niaeashes/prmd,araines/prmd,interagent/prmd,junya-i/prmd,shopkeep/prmd,mykecameron/prmd,mykecameron/prmd,hx/prmd,junya-i/prmd,hmac/prmd,michaelsauter/prmd,robhurring/prmd,interagent/prmd,uberjay/prmd,MobileDevHQ/prmd,araines/prmd,ruprict/prmd,niaeashes/prmd,hmac/prmd,michaelsauter/prmd,ruprict/prmd,IceDragon200/prmd,hx/prmd,robhurring/prmd