Possible fix for not being able to run vagrant up under OSX
Possible fix for not being able to run vagrant up under OSX

* added troubleshooting section to vagrant.md

* fixed Header 4 formatting and created markdown link

leahphuong/leahphuong.github.io,leahphuong/leahphuong.github.io,leahphuong/leahphuong.github.io