Add instructions for getting Gerrit HTTP password to contributing.md
Add instructions for getting Gerrit HTTP password to contributing.md

This will help contributors who only read one level of docs, like
myself!

--
Reviewed-on: https://github.com/google/bazel/pull/316
MOS_MIGRATED_REVID=98829887

twitter-forks/bazel,vt09/bazel,mikelalcon/bazel,safarmer/bazel,ButterflyNetwork/bazel,spxtr/bazel,abergmeier-dsfishlabs/bazel,UrbanCompass/bazel,Asana/bazel,dropbox/bazel,dslomov/bazel,JackSullivan/bazel,perezd/bazel,bitemyapp/bazel,whuwxl/bazel,iamthearm/bazel,joshua0pang/bazel,murugamsm/bazel,iamthearm/bazel,kchodorow/bazel-1,bazelbuild/bazel,dinowernli/bazel,twitter-forks/bazel,xindaya/bazel,iamthearm/bazel,abergmeier-dsfishlabs/bazel,kchodorow/bazel,Krasnyanskiy/bazel,manashmndl/bazel,joshua0pang/bazel,perezd/bazel,sicipio/bazel,nkhuyu/bazel,kchodorow/bazel-1,davidzchen/bazel,bitemyapp/bazel,spxtr/bazel,damienmg/bazel,mikelikespie/bazel,rhuss/bazel,kamalmarhubi/bazel,meteorcloudy/bazel,katre/bazel,akira-baruah/bazel,whuwxl/bazel,mrdomino/bazel,LuminateWireless/bazel,sicipio/bazel,twitter-forks/bazel,mrdomino/bazel,safarmer/bazel,manashmndl/bazel,JackSullivan/bazel,dhootha/bazel,charlieaustin/bazel,Topher-the-Geek/bazel,Topher-the-Geek/bazel,juhalindfors/bazel-patches,dslomov/bazel,Topher-the-Geek/bazel,davidzchen/bazel,katre/bazel,hermione521/bazel,mbrukman/bazel,dropbox/bazel,mikelikespie/bazel,UrbanCompass/bazel,snnn/bazel,Asana/bazel,d/bazel,zhexuany/bazel,variac/bazel,ruo91/bazel,sicipio/bazel,werkt/bazel,Asana/bazel,vt09/bazel,spxtr/bazel,rhuss/bazel,zhexuany/bazel,Topher-the-Geek/bazel,Ansahmadiba/bazel,meteorcloudy/bazel,dhootha/bazel,katre/bazel,bitemyapp/bazel,manashmndl/bazel,bazelbuild/bazel,kchodorow/bazel,werkt/bazel,vt09/bazel,dhootha/bazel,charlieaustin/bazel,damienmg/bazel,snnn/bazel,wakashige/bazel,anupcshan/bazel,wakashige/bazel,Ansahmadiba/bazel,vt09/bazel,mikelalcon/bazel,d/bazel,anupcshan/bazel,abergmeier-dsfishlabs/bazel,ruo91/bazel,hermione521/bazel,Digas29/bazel,iamthearm/bazel,joshua0pang/bazel,joshua0pang/bazel,davidzchen/bazel,snnn/bazel,UrbanCompass/bazel,bazelbuild/bazel,abergmeier-dsfishlabs/bazel,vt09/bazel,damienmg/bazel,kchodorow/bazel-1,murugamsm/bazel,ulfjack/bazel,LuminateWireless/bazel,nkhuyu/bazel,hhclam/bazel,sicipio/bazel,charlieaustin/bazel,mbrukman/bazel,Asana/bazel,hermione521/bazel,safarmer/bazel,asarazan/bazel,LuminateWireless/bazel,asarazan/bazel,LuminateWireless/bazel,mikelalcon/bazel,kchodorow/bazel,twitter-forks/bazel,kchodorow/bazel,dinowernli/bazel,d/bazel,ButterflyNetwork/bazel,charlieaustin/bazel,akira-baruah/bazel,mbrukman/bazel,Ansahmadiba/bazel,nkhuyu/bazel,ruo91/bazel,safarmer/bazel,manashmndl/bazel,ulfjack/bazel,meteorcloudy/bazel,akira-baruah/bazel,dslomov/bazel-windows,wakashige/bazel,asarazan/bazel,perezd/bazel,aehlig/bazel,snnn/bazel,kchodorow/bazel,UrbanCompass/bazel,murugamsm/bazel,Ansahmadiba/bazel,hhclam/bazel,ButterflyNetwork/bazel,Ansahmadiba/bazel,katre/bazel,Asana/bazel,twitter-forks/bazel,zhexuany/bazel,perezd/bazel,juhalindfors/bazel-patches,mikelalcon/bazel,katre/bazel,snnn/bazel,cushon/bazel,joshua0pang/bazel,ButterflyNetwork/bazel,bazelbuild/bazel,kamalmarhubi/bazel,Ansahmadiba/bazel,hhclam/bazel,dinowernli/bazel,rohitsaboo/bazel,Krasnyanskiy/bazel,mrdomino/bazel,ruo91/bazel,Krasnyanskiy/bazel,mikelikespie/bazel,snnn/bazel,akira-baruah/bazel,dslomov/bazel-windows,bitemyapp/bazel,dinowernli/bazel,wakashige/bazel,dinowernli/bazel,werkt/bazel,bazelbuild/bazel,anupcshan/bazel,variac/bazel,murugamsm/bazel,joshua0pang/bazel,kchodorow/bazel,charlieaustin/bazel,d/bazel,charlieaustin/bazel,hhclam/bazel,dslomov/bazel,variac/bazel,murugamsm/bazel,werkt/bazel,murugamsm/bazel,Topher-the-Geek/bazel,JackSullivan/bazel,meteorcloudy/bazel,xindaya/bazel,Digas29/bazel,xindaya/bazel,aehlig/bazel,ruo91/bazel,variac/bazel,zhexuany/bazel,manashmndl/bazel,ulfjack/bazel,asarazan/bazel,davidzchen/bazel,mbrukman/bazel,zhexuany/bazel,spxtr/bazel,dslomov/bazel-windows,murugamsm/bazel,dslomov/bazel-windows,Krasnyanskiy/bazel,werkt/bazel,dropbox/bazel,perezd/bazel,dhootha/bazel,damienmg/bazel,akira-baruah/bazel,dropbox/bazel,anupcshan/bazel,dinowernli/bazel,katre/bazel,perezd/bazel,manashmndl/bazel,spxtr/bazel,Digas29/bazel,mrdomino/bazel,Krasnyanskiy/bazel,wakashige/bazel,twitter-forks/bazel,hermione521/bazel,juhalindfors/bazel-patches,bitemyapp/bazel,zhexuany/bazel,juhalindfors/bazel-patches,UrbanCompass/bazel,ButterflyNetwork/bazel,JackSullivan/bazel,dropbox/bazel,Asana/bazel,aehlig/bazel,werkt/bazel,dropbox/bazel,ulfjack/bazel,Krasnyanskiy/bazel,hermione521/bazel,aehlig/bazel,juhalindfors/bazel-patches,Digas29/bazel,JackSullivan/bazel,xindaya/bazel,xindaya/bazel,rohitsaboo/bazel,juhalindfors/bazel-patches,twitter-forks/bazel,iamthearm/bazel,manashmndl/bazel,ulfjack/bazel,meteorcloudy/bazel,akira-baruah/bazel,charlieaustin/bazel,rhuss/bazel,mikelikespie/bazel,rohitsaboo/bazel,Topher-the-Geek/bazel,asarazan/bazel,ulfjack/bazel,damienmg/bazel,ruo91/bazel,mrdomino/bazel,damienmg/bazel,rhuss/bazel,bazelbuild/bazel,rhuss/bazel,d/bazel,Topher-the-Geek/bazel,mikelalcon/bazel,davidzchen/bazel,davidzchen/bazel,safarmer/bazel,whuwxl/bazel,joshua0pang/bazel,dslomov/bazel,cushon/bazel,aehlig/bazel,abergmeier-dsfishlabs/bazel,anupcshan/bazel,dslomov/bazel,vt09/bazel,kchodorow/bazel-1,Digas29/bazel,kamalmarhubi/bazel,spxtr/bazel,asarazan/bazel,damienmg/bazel,ulfjack/bazel,xindaya/bazel,meteorcloudy/bazel,dhootha/bazel,abergmeier-dsfishlabs/bazel,meteorcloudy/bazel,variac/bazel,dslomov/bazel,cushon/bazel,whuwxl/bazel,kamalmarhubi/bazel,spxtr/bazel,dslomov/bazel-windows,safarmer/bazel,aehlig/bazel,mikelikespie/bazel,davidzchen/bazel,dslomov/bazel,Asana/bazel,kchodorow/bazel-1,rhuss/bazel,sicipio/bazel,nkhuyu/bazel,bitemyapp/bazel,Topher-the-Geek/bazel,anupcshan/bazel,snnn/bazel,mikelalcon/bazel,LuminateWireless/bazel,Krasnyanskiy/bazel,nkhuyu/bazel,cushon/bazel,hhclam/bazel,d/bazel,Ansahmadiba/bazel,kamalmarhubi/bazel,d/bazel,ButterflyNetwork/bazel,whuwxl/bazel,hhclam/bazel,hermione521/bazel,dhootha/bazel,whuwxl/bazel,aehlig/bazel,rohitsaboo/bazel,variac/bazel,variac/bazel,kchodorow/bazel-1,bitemyapp/bazel,Krasnyanskiy/bazel,LuminateWireless/bazel,mikelikespie/bazel,sicipio/bazel,asarazan/bazel,dslomov/bazel-windows,juhalindfors/bazel-patches,iamthearm/bazel,mbrukman/bazel,nkhuyu/bazel,rohitsaboo/bazel,wakashige/bazel,cushon/bazel,xindaya/bazel,kchodorow/bazel,rohitsaboo/bazel,bitemyapp/bazel,JackSullivan/bazel,mrdomino/bazel,JackSullivan/bazel,kamalmarhubi/bazel,ruo91/bazel,perezd/bazel,Digas29/bazel,wakashige/bazel,UrbanCompass/bazel,mbrukman/bazel,nkhuyu/bazel,sicipio/bazel,cushon/bazel,rhuss/bazel,dhootha/bazel,vt09/bazel