add path levels for absolute paths on windows

[dpastoor]

Right now just checking for / but if they have C:/... for a data path, will end up expanding to ../C:/ which obviously isn't valid.

As not going to be using windows personally, noting this to visit but is low priority to use. Should use relative paths anyway.

[dpastoor]

To be more clear, this is in regards to adding additional levels to the path in $DATA when moving model files around before estimation