* - Verify that the state received alongside the authorization code is consistent with the one sent
- Refactor URL parsing for the local server way and the interactive way
- Add tests for interactive way
* Resurrect public methods parse_response_code and get_authorization_code
* Use new method parse_oatuh_response_url for parse_response_code implementation.
- add error and error description to SpotifyOauthError to reflect the data returned by web api when error happens
- unit test to SpotifyClientCredentials.get_access_token is added for invalid client
* Linting of OAuth2 mod. + update tests to detect core package path
* Tweak imports in tests + update tox ini to ignore Flake8 E501 error
* Tweak tox ini - ignore examples
* Remove `f`-string from OAuth2 mod.
* More import tweaks in core package + tests
* Update flake8 config. in tox ini - set line length limit to 99 chars.
