(pub): publish v0.0.4

- adds django_serializable_model module
  - previously had to import via serializable module, which was
    unintuitive and unintentional
    - can still use serializable module if you were using it before;
      there are no breaking changes made in this patch release, but
      it is deprecated and will be removed when v1.0.0 rolls around
- fixes incorrect module name used in Usage docs

- adds CHANGELOG.md
- adds Django 2.2 classifier
- some other minor docs improvements around badges and clarifications

- purely internal changes:
  - adds changelog.sh script

setup.py

@@ -13,7 +13,7 @@
 
 setup(
     name='django-serializable-model',
-    version='0.0.3',
+    version='0.0.4',
     description=('Django classes to make your models, managers, and ' +
                  'querysets serializable, with built-in support for related ' +
                  'objects in ~100 LoC'),