Adds more rules to mypy config, related #662 (#663)

* Adds more rules to mypy config, related #662

* Removes plugin.ini for mypy settings

* Fixes build

mypy.ini

@@ -1,11 +1,14 @@
 [mypy]
-strict_optional = True
-ignore_missing_imports = True
-check_untyped_defs = True
-warn_no_return = False
-show_traceback = True
 allow_redefinition = True
+check_untyped_defs = True
+ignore_missing_imports = True
 incremental = True
+strict_optional = True
+show_traceback = True
+warn_no_return = False
+warn_unused_ignores = True
+warn_redundant_casts = True
+warn_unused_configs = True
 
 plugins =
     mypy_django_plugin.main