Fix broken link due to googlecode retirement.
Fix broken link due to googlecode retirement.

The previous link to the gtest-1.7.0 zip was broken, making it difficult for a user to follow-along with the documentation.  Project has been moved to github, links and prefixes updated accordingly.

Closes #1688.

--
Reviewed-on: https://github.com/bazelbuild/bazel/pull/1688
MOS_MIGRATED_REVID=133572103

dslomov/bazel,Asana/bazel,perezd/bazel,katre/bazel,aehlig/bazel,ulfjack/bazel,ulfjack/bazel,variac/bazel,kchodorow/bazel,Asana/bazel,aehlig/bazel,zhexuany/bazel,safarmer/bazel,perezd/bazel,dslomov/bazel,davidzchen/bazel,mrdomino/bazel,zhexuany/bazel,juhalindfors/bazel-patches,iamthearm/bazel,twitter-forks/bazel,snnn/bazel,ButterflyNetwork/bazel,twitter-forks/bazel,zhexuany/bazel,zhexuany/bazel,hermione521/bazel,mrdomino/bazel,twitter-forks/bazel,hermione521/bazel,ulfjack/bazel,LuminateWireless/bazel,safarmer/bazel,mbrukman/bazel,mikelikespie/bazel,kchodorow/bazel,snnn/bazel,akira-baruah/bazel,ButterflyNetwork/bazel,cushon/bazel,dslomov/bazel,spxtr/bazel,mbrukman/bazel,ButterflyNetwork/bazel,LuminateWireless/bazel,twitter-forks/bazel,Asana/bazel,zhexuany/bazel,mbrukman/bazel,perezd/bazel,dslomov/bazel,mrdomino/bazel,damienmg/bazel,spxtr/bazel,kchodorow/bazel,katre/bazel,ButterflyNetwork/bazel,variac/bazel,snnn/bazel,kchodorow/bazel-1,akira-baruah/bazel,dropbox/bazel,perezd/bazel,aehlig/bazel,davidzchen/bazel,twitter-forks/bazel,cushon/bazel,iamthearm/bazel,dslomov/bazel,cushon/bazel,ulfjack/bazel,spxtr/bazel,kchodorow/bazel,perezd/bazel,werkt/bazel,dslomov/bazel-windows,twitter-forks/bazel,bazelbuild/bazel,davidzchen/bazel,dslomov/bazel,bazelbuild/bazel,damienmg/bazel,safarmer/bazel,spxtr/bazel,Asana/bazel,werkt/bazel,mrdomino/bazel,damienmg/bazel,snnn/bazel,mbrukman/bazel,ulfjack/bazel,mrdomino/bazel,davidzchen/bazel,perezd/bazel,hermione521/bazel,juhalindfors/bazel-patches,cushon/bazel,safarmer/bazel,safarmer/bazel,twitter-forks/bazel,dropbox/bazel,damienmg/bazel,akira-baruah/bazel,aehlig/bazel,hermione521/bazel,davidzchen/bazel,kchodorow/bazel-1,mikelikespie/bazel,damienmg/bazel,katre/bazel,mikelikespie/bazel,mikelikespie/bazel,bazelbuild/bazel,meteorcloudy/bazel,kchodorow/bazel-1,spxtr/bazel,ulfjack/bazel,LuminateWireless/bazel,variac/bazel,dslomov/bazel-windows,werkt/bazel,ButterflyNetwork/bazel,juhalindfors/bazel-patches,juhalindfors/bazel-patches,mikelikespie/bazel,LuminateWireless/bazel,juhalindfors/bazel-patches,meteorcloudy/bazel,werkt/bazel,dropbox/bazel,snnn/bazel,meteorcloudy/bazel,kchodorow/bazel-1,dropbox/bazel,cushon/bazel,hermione521/bazel,katre/bazel,davidzchen/bazel,mbrukman/bazel,snnn/bazel,iamthearm/bazel,kchodorow/bazel,akira-baruah/bazel,juhalindfors/bazel-patches,hermione521/bazel,variac/bazel,safarmer/bazel,werkt/bazel,Asana/bazel,akira-baruah/bazel,dropbox/bazel,snnn/bazel,spxtr/bazel,werkt/bazel,juhalindfors/bazel-patches,meteorcloudy/bazel,cushon/bazel,dslomov/bazel-windows,variac/bazel,zhexuany/bazel,ulfjack/bazel,katre/bazel,kchodorow/bazel,dslomov/bazel,bazelbuild/bazel,damienmg/bazel,variac/bazel,akira-baruah/bazel,ButterflyNetwork/bazel,mikelikespie/bazel,mrdomino/bazel,Asana/bazel,mbrukman/bazel,kchodorow/bazel-1,aehlig/bazel,dslomov/bazel-windows,iamthearm/bazel,meteorcloudy/bazel,kchodorow/bazel-1,dslomov/bazel-windows,bazelbuild/bazel,dslomov/bazel-windows,spxtr/bazel,iamthearm/bazel,katre/bazel,bazelbuild/bazel,aehlig/bazel,meteorcloudy/bazel,aehlig/bazel,Asana/bazel,damienmg/bazel,davidzchen/bazel,variac/bazel,perezd/bazel,LuminateWireless/bazel,iamthearm/bazel,dropbox/bazel,LuminateWireless/bazel,meteorcloudy/bazel,kchodorow/bazel