Scrapy-deltafetch

------------------
* drop Python 2 support
* replace bsddb3 with Python's dbm for storing request fingerprints
* minor README fix
* option to disable deltafetch for some requests with deltafetch_enabled=False request meta key
* dev workflow: changed from Travis to Github Actions

------------------

* Use python idiom to check key in dict
* Update minimum Scrapy version supported by this extension to v1.1.0

------------------

* Log through ``logging`` module instead of (deprecated) scrapy's spider.log().
* Fix README on passing ``deltafetch_reset`` argument on the command line.

------------------

Adds support for callbacks returning dict items.

------------------

Fix package URL in setup.py

------------------

Initial release.

This version is functionally equivalent to scrapylib's v1.7.0
``scrapylib.deltafetch.DeltaFetch``.

The only (and major) difference is that support for ``bsddb`` is dropped
in favor of ``bsddb3``, which is a new required dependency.

.. note::
`bsddb`_ has been deprecated since Python 2.6,
and even removed in Python 3


.. _bsddb: https://docs.python.org/2/library/bsddb.html