Changelog 3.2.0

Add CORS support for Refresh Token Grant.

GitHub Action to lint Python code

* Fix list of current features for 3.2.0

* Renamed travis-ci.org icon URLs

* Force fixing the warnings in the docs generation

* Removed unused folder reference

* Added orphean documents into summary.

* Fix docstring formatting example in contributing page.

* Removed unused argument from documentation

* Fix sphinx warning resulting in loss of formatting in RTD.

* Force setuptools until pypa/setuptools#3118 is fixed

* Prevent linux redirection in travis instructions

* Add graphviz/dot command to generate docs frmo Travis

* Allow non-HTTPS issuer when OAUTHLIB_INSECURE_TRANSPORT.

* Add unit test for validating issuer.

missing semicolon

tox runs isort, whicn pointed multiple errors.
Fixed them in this PR

There are small typos in:
- docs/oauth1/security.rst
- docs/oauth2/grants/custom_grant.rst
- oauthlib/oauth2/rfc6749/clients/backend_application.py
- oauthlib/oauth2/rfc6749/clients/base.py
- oauthlib/oauth2/rfc6749/clients/legacy_application.py
- oauthlib/oauth2/rfc6749/clients/service_application.py
- oauthlib/oauth2/rfc6749/clients/web_application.py
- oauthlib/oauth2/rfc6749/endpoints/revocation.py
- oauthlib/oauth2/rfc6749/parameters.py
- oauthlib/openid/connect/core/grant_types/dispatchers.py

Fixes:
- Should read `parameters` rather than `paramters`.
- Should read `instantiate` rather than `instanciate`.
- Should read `successfully` rather than `sucessfully`.
- Should read `present` rather than `pressent`.
- Should read `parameter` rather than `paramater`.
- Should read `efficient` rather than `effecient`.