nfs: true vs type: "nfs"

closes https://github.com/roots/bedrock-ansible/issues/71

Fix msg: chown failed when vagrant up

closes https://github.com/roots/bedrock-ansible/issues/70

https://github.com/roots/bedrock-ansible/issues/70#issuecomment-57748400
Merge pull request #72 from austinpray/master

Fix chown errors on vagrant up