bump version, more tests, update docs

docs_src/signals/docs002.py

@@ -0,0 +1,22 @@
+from ormar import pre_update
+
+
+@pre_update(Album)
+async def before_update(sender, instance, **kwargs):
+    if instance.play_count > 50 and not instance.is_best_seller:
+        instance.is_best_seller = True
+
+
+# here album.play_count ans is_best_seller get default values
+album = await Album.objects.create(name="Venice")
+assert not album.is_best_seller
+assert album.play_count == 0
+
+album.play_count = 30
+# here a trigger is called but play_count is too low
+await album.update()
+assert not album.is_best_seller
+
+album.play_count = 60
+await album.update()
+assert album.is_best_seller