update bob dependency to point to internal bob-builder fork
update bob dependency to point to internal bob-builder fork

ad-m/heroku-buildpack-python,heroku/heroku-buildpack-python,benjaminfox/heroku-buildpack-python-geoip,benmurden/heroku-buildpack-python-ember,heroku/heroku-buildpack-python,Scalingo/python-buildpack,AltSchool/heroku-buildpack-python,benmurden/heroku-buildpack-python-ember,ad-m/heroku-buildpack-python,benjaminfox/heroku-buildpack-python-geoip,skilljar/heroku-buildpack-python,Scalingo/python-buildpack,AltSchool/heroku-buildpack-python