Commonpy

Changes in this release:
* Revise the retry algorithm in `timed_request()` again.
* Make `timed_request()` print the response text in case of failures
* Remove `extra_requires` from `setup.py` because it caused installation problems due to the syntax of the requirements file and I don't have patience for figuring out what `setuptools` needs this time.

This release updates the version of the `dateparser` package in `requirements.txt`, to avoid a deprecation warning when using CommonPy's `parsed_datetime(...)` function.

This release updates the versions of dependencies in `requirements.txt`.

This version prevents certain exceptions from being buried and ignored, and improves the network failure retry algorithm.

Additions in this release:
* New function `network` in the `network_utils` module. It is a companion to `net` and takes the same arguments, but returns only one value (the response). If an error occurs, it raises the error as an exception. This makes it possible for callers to use `network(...)` in somewhat more Pythonic style than `net(...)`, by wrapping the call to `network(...)` in `try`-`except`.

Changes in this release:
* Removed `slice` from `data_utils` module because it shadows a Python built-in.
* Fixed `hostname` in `network_utils` to be more general and not hardwire a test for `http`.
* Fixed a bunch of `flake8` warnings.

Additions in this release:
* New class `CaseFoldSet`, similar to `CaseFoldDict` but … a set.

Changes in this release:
* Fixed a bug in the class documentation in the `README.md` file.
* Added missing dependency for [twine]() in requirements-dev
* Now using lazy `import`s in more places, for faster load times.