Fix backward compatibility for earthpy data subsets

Author: eculler

earthpy/io.py

@@ -353,7 +353,7 @@ def _download(self, url, path, kind, replace, verbose):
         output_path : str
             Path to the downloaded file.
         """
-        path = self.project.project_dir / path
+        path = self.path / path
         if replace is False and path.exists():
             return path