Update Readme for new linter ignore migration operation

Use master for PRs. No need for a dev branch

README.rst

@@ -52,20 +52,20 @@ Examples
 3YOURMIND is running the linter on `Bitbucket Pipelines`_ on every build getting pushed.
 Checkout the ``examples/`` folder to see how you could integrate the linter in your test suite.
 
-Ignoring Migrations
+Ignoring migrations
 -------------------
 
 You can also ignore migrations by adding this to your migrations:
 
 .. code-block::
 
-    from django_migration_linter import IGNORE_MIGRATION
+    import django_migration_linter as linter
     # ...
 
-       operations = [
-            migrations.RunSQL(IGNORE_MIGRATION),
-       # ...
-       ]
+        operations = [
+            linter.IgnoreMigration(),
+            # ...
+        ]
     # ...
 
 
@@ -78,7 +78,7 @@ Contributing
 ------------
 
 First, thank you very much if you want to contribute to the project.
-Please base your work on the ``dev`` branch and also target this branch in your pull request.
+Please base your work on the ``master`` branch and also target this branch in your pull request.
 
 License
 -------