Change readme to fix RST rendering issue. Add unit tests to prevent this in the future.

Author: ertukara

README.rst

@@ -559,10 +559,6 @@ The following are details about the warnings you might see:
 
 For more information, see http://www.gnupg.org.
 
-.. |codebuild| image:: https://codebuild.us-east-2.amazonaws.com/badges?uuid=eyJlbmNyeXB0ZWREYXRhIjoiZ2crZkxWN2lPTHhBdzAwOUIvZDlUQ2txQTRyYnZnQ3RaQ0dQYkhsb2EvT04xOVRIdDBqYWFOaS8weklGU216OUtuc29pZFQvQjgrRDhRbWJoeEJocFV3PSIsIml2UGFyYW1ldGVyU3BlYyI6IlRQUlZQd1ZLdGRqWkdVdWkiLCJtYXRlcmlhbFNldFNlcmlhbCI6MX0%3D&branch=master
- :target: https://us-east-2.console.aws.amazon.com/codesuite/codebuild/projects/StepFunctionsPythonSDK-unittests-private/history?region=us-east-2
- :alt: Unit Tests Build Status
-
 .. |codebuild| image:: https://codebuild.us-east-2.amazonaws.com/badges?uuid=eyJlbmNyeXB0ZWREYXRhIjoiZ2crZkxWN2lPTHhBdzAwOUIvZDlUQ2txQTRyYnZnQ3RaQ0dQYkhsb2EvT04xOVRIdDBqYWFOaS8weklGU216OUtuc29pZFQvQjgrRDhRbWJoeEJocFV3PSIsIml2UGFyYW1ldGVyU3BlYyI6IlRQUlZQd1ZLdGRqWkdVdWkiLCJtYXRlcmlhbFNldFNlcmlhbCI6MX0%3D&branch=master
  :target: https://us-east-2.console.aws.amazon.com/codesuite/codebuild/projects/StepFunctionsPythonSDK-unittests-private/history?region=us-east-2
  :alt: Unit Tests Build Status

buildspec_unit.yaml

@@ -3,7 +3,10 @@ version: 0.2
 phases:
  pre_build:
  commands:
+ - pip install steuptools wheel twine
+ - python setup.py bdist_wheel
  - pip install tox
  build:
  commands:
+ - twine check dist dist/*
  - tox tests/unit/