Adding setup instructions for RHEL and RHEL derivatives
Pull vows via https, not git protocol

hardik in IRC had a ton of trouble installing Persona because of this. For some
reason he wasn't able to clone over git://, but https works just fine.

This should also be marginally faster since we don't have to clone an entire
repo.
Merge pull request #4061 from gene1wood/dev

Adding setup instructions for RHEL and RHEL derivatives
Merge pull request #4062 from mozilla/deps

Pull vows via https, not git protocol