Merge master changes instead of rebasing

Previous rebasing doesn't play well with an upstream copy It's clean and
nice on the local work environment but I have to stop rebasing and push
--force now that others start using the repo...
Update README : Info on Unity / memory req. + Misc.
Merge "Minor MarkDown fixes to display properly on GitHub"

Thanks to original commit:
Signed-off-by: Gianpaolo Macario <gianpaolo_macario@mentor.com>
8f23e307ab298627905c45b9d7f82348d8a66219

My history had changed a bit (I probably rebased something)
so it was easier to do a manual merge.
Use markup for code blocks in README
Cleaned and reindented Vagrantfile with 3 spaces, remove tabs
Weird provisioning bug, counteract with explicit --provision flag

vagrant destroy + vagrant up, should surely provision the new fresh
machine, but under certain circumstances Vagrant seems to claim that the
machine is already provisioned.  It appears this weird bug can be
circumvented by simply forcing provisioning.  Still have no idea
why this happens though - it didn't do it before...
Merge also upstream so we can push properly