Add Migration class to hold the path, app name and migration name in one object + adapt existing logic

django_migration_linter/migration.py

@@ -0,0 +1,7 @@
+from django_migration_linter.utils import split_migration_path
+
+
+class Migration(object):
+    def __init__(self, abs_path):
+        self.abs_path = abs_path
+        self.app_name, self.name = split_migration_path(self.abs_path)