Update Readme about installing on Mavericks and Mountain Lion 

I just reinstalled Mountain Lion 10.8.5, and I only needed the extra file, and not to do any of the steps from part 1. So I've tested it both on fresh install of Mavericks 10.9 and Mountain Lion 10.8.5. Both installed CalCentral with no problem.
Merge pull request #1753 from jmanalus/patch-2

Update Readme about installing on Mavericks and Mountain Lion