Move importers into module

bookwyrm/importers/goodreads_import.py

@@ -0,0 +1,16 @@
+""" handle reading a csv from goodreads """
+from . import Importer
+
+
+class GoodreadsImporter(Importer):
+    """GoodReads is the default importer, thus Importer follows its structure.
+    For a more complete example of overriding see librarything_import.py"""
+
+    service = "GoodReads"
+
+    def parse_fields(self, entry):
+        """ handle the specific fields in goodreads csvs """
+        entry.update({"import_source": self.service})
+        # add missing 'Date Started' field
+        entry.update({"Date Started": None})
+        return entry