Add Homestead.sample.yaml  and ignore Homestead.yaml for easier updating

I wanted to get the updates for the new homestead files.  I had to stash my configuration of my Homestead.yaml file because it was trying to overwrite mine.   I am suggesting here that you create a Homestead.sample.yaml file and have instructions to copy it to Homestead.yaml.  This will allow you to do a git update easier.