* Pass `**kwargs` to backend storage classes, split out any that are valid for the backend-specific connection function/class, and pass them to the connection
* Add intersphinx links to docs for dependencies
* Update and format some more backend class docstrings
* Remove 'Unrecognized keyword arguments' warning from `BaseStorage`
* Turn `warnings.warn` about using secret keys into a `logging.warning` (due to complaints about too many messages)

See:
* https://github.com/sphinx-doc/sphinx/issues/9001
* https://github.com/readthedocs/sphinx_rtd_theme/issues/1112

* Use sphinx-apidoc to auto-generate sources for backend modules
    * Still manually adding other modules for more control over formatting
* Add a couple more contributors I missed
* Include contributors on readthedocs
* Add 'all' Makefile target and clean auto-generated docs
* Remove unused build targets in Makefile
* Update interpshinx links that have moved
* Fix some interpshinx links
* Fix some `:ref:` links using auto-generated labels (and some manually added labels where convenient)
* Fix some docstring formatting
* Fix remaining build warnings

* Closes #135, #165
* Add a 'Summary' section at the top of the Readme explaining the scope of requests-cache and why you would want to use it
* Add some more info explaining the difference between using `CachedSession` directly vs. patching with `install_cache()`
* Move basic examples from 'User Guide' section into Readme
* Include Readme in Sphinx docs (using `.. mdinclude::`) and remove duplicate sections
* Include Contributing guide in Sphinx docs
* Convert History doc to markdown and include in Sphinx docs
* Use `automod` options to move main cache documentation from `CacheMixin` back to to `CachedSession`, since that's probably where a user will look first
* Add more detailed usage examples to an 'Advanced Usage' section for `CachedSession` options (`filter_fn`, `ignore_parameters`, etc.)
* Update example scripts and move them to `examples/` folder

* Add individual expire_after per request.

This commit adds a new feature to allow individual expire_after times
per request.
It involves using a custom CachedSession, PerRequestCachedSession,
to be used as the session_factory.

* Replace deprecated asserts in unit tests

Additionally, some sockets are closed even on test failures.
This removes some visual clutter when going through the results.

* Update docs and README for per-request caching

* Remove per_request and integrate behavior into CachedSession

* Make test_return_old_data_on_error more reliable

This is achieved by using a fixed date and mocking the backend calls to datetime as well.

* Adjust per_request cache to new behavior

Also adds HTTPBIN_URL environment variable as in test_cache

* Add tests for the function determining the expiration datetime

* Adjust backend to store expiration dates

This also involves slightly different semantics for deletion, but the behavior stays the same.

* Minor: black and isort

* Update docs for request

Add explanation for expire_after special cases, i.e. 'default' and 'cached' and how precedences are handled

* Replace assert statements with methods

* Remove invalid snippet from README

* Remove invalid sentence from docs.

* Make expires_before timezone-aware once

And combine the checks for expiration

* Simplify complexity by removing 'cached' keyword for expire_after

* Add `.readthedocs.yml` build config
* Remove mocks for backend modules (pymongo, redis-py, etc.), and make Readthedocs install them before building
* Add Sphinx extensions for:
    * Google-style docstrings
    * 'Copy' button for code snippets
    * Automatic type annotation docs
    * Links to view source code
* Add documentation requirements to setup.py for building docs locally
* Remove config for unused Sphinx outputs