Better typeahead sorting for rare words

Not all words have a rel_importance value. For those, we should assume a
low relative importance. Before, the information from max_score got lost
because it was multiplied wit the rel_importance value.

This has even more impact than it should have, since the current
deployment misses many rel_importance values due to
karlb/wikdict-gen@4058c97 .

Closes #8.

wikdict_web/typeahead.py

@@ -16,7 +16,7 @@ def get_typeahead_data(from_lang, to_lang, query, limit=None):
             FROM other.simple_translation
             WHERE written_rep LIKE :query || '%'
         )
-        ORDER BY max_score * rel_importance DESC
+        ORDER BY max_score * coalesce(rel_importance, 0.01) DESC
     """
     if limit:
         sql += ' LIMIT {}'.format(limit)