fixes #14 windows devstack support

This
 * adds a note to compensate missing symlink support in Windows
 * adds a note in regard to having to manually configure /etc/hosts on
   Windows (we should have a look at vagrant-hostmanager)
 * fixes some path handling which causes vagrant commands from a subdir
   to fail
Merge pull request #16 from Mayflower/windows-support

Windows Devstack Support