Fix tests status badge (#897)

README.rst

@@ -6,8 +6,8 @@ PynamoDB
     :target: https://pypi.python.org/pypi/pynamodb/
 .. image:: https://img.shields.io/conda/vn/conda-forge/pynamodb.svg
     :target: https://anaconda.org/conda-forge/pynamodb
-.. image:: https://img.shields.io/travis/pynamodb/PynamoDB/master.svg
-    :target: https://travis-ci.org/pynamodb/PynamoDB
+.. image:: https://github.com/pynamodb/PynamoDB/workflows/Tests/badge.svg
+    :target: https://github.com/pynamodb/PynamoDB/actions
 .. image:: https://img.shields.io/coveralls/pynamodb/PynamoDB/master.svg
     :target: https://coveralls.io/r/pynamodb/PynamoDB
 

docs/release_notes.rst

@@ -13,13 +13,13 @@ This is major release and contains breaking changes. Please read the notes below
 This release introduces :ref:`polymorphism` support via :py:class:`DiscriminatorAttribute <pynamodb.attributes.DiscriminatorAttribute>`.
 Discriminator values are written to DynamoDB and used during deserialization to instantiate the desired class.
 
-** UTCDateTimeAttribute **
+**UTCDateTimeAttribute**
 
 The UTCDateTimeAttribute now strictly requires the date string format '%Y-%m-%dT%H:%M:%S.%f%z' to ensure proper ordering.
 PynamoDB has always written values with this format but previously would accept reading other formats.
 Items written using other formats must be rewritten before upgrading.
 
-** Model Serialization **
+**Model Serialization**
 
 THe ``Model`` class now includes public methods for serializing and deserializing its attributes.
 ``Model.serialize`` and ``Model.deserialize`` convert the model to/from a dictionary of DynamoDB attribute values.