MSAL Python 1.4.0

[abhidnya13]

Each of the features/bugfixes included in this release has been tested, reviewed and approved in their individual PR. The purpose of this all-in-one release PR is to organize the release process. Please review/proof-read the following release notes.

Release Notes:

• Enhancement: Application initializer will not send network requests. (Application initializer does not make tenant discovery calls #205, ClientApplication initializer sends HTTP requests #187)
• Enhancement: Improved handling of errors in ADAL to MSAL token migration scenario. (Migration should fail gracefully even on wrong RT #209, acquire_token_by_refresh_token - AttributeError: 'str' object has no attribute 'get' #208)
• Added changelog in PYPI (Use release history as changelog for PyPI #203, Changelog #202)
• Other readme and reference docs adjustments (One of the examples in the README was not legal python syntax. #200, Changing format of domain_hint links in docstring #197)

If you prefer to, you can install this branch for your smoke testing:

pip install git+https://github.com/AzureAD/microsoft-authentication-library-for-python.git@release-1.4.0

[rayluo]

Looks good!
Please merge WITHOUT squashing.