Prevent foreman export from expanding the current/ symlink

`foreman export` will default to using `Dir.pwd` as the projects directory. Unfortunately, `Dir.pwd` automatically expands symlinks to their destinations, so `/path/to/current` becomes `/path/to/releases/N`. Instead, explicitly specify the `/path/to/current/`.
Merge pull request #241 from postmodern/patch-2

Prevent foreman export from expanding the current/ symlink